Gunpowder

Falls

Maryland

USES OF A WATER RESOURCE 

TODAY AND TOMORROW

By DERIC O'BRYAN 

and RUSSELL L McAVOY

An ana lysis

of the major

demands on the

Gunpowder Fal I s

basin : living

space, water

supply, and

recreation

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1815
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L UDALL, Secretary

GEOLOGICAL SURVEY 

William T, Pecora, Director

Library of Congress catalog-card No. GS 65-370

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1966

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 - Price 45 cents (paper cover)
Contents

Page

Introduction._____________________________________________________ 1

What the basin provides today._____________________________________ 3

Living space._________________________________________________ 3

Location________________________________________________ 3

History __________________________________________________ 5

Population___ __________________________________________ 7

Economics.._ _____________________________________________ 7

Roads__________________________________________________ 10

Water resource.__---_---____________--____________-_-_________ 10

Water, a variable commodity._____-__-_____-____---___-____ 11

Averages and probabilities__________-__-____-___-_----_____- 14

Public supply for Metropolitan Baltimore____________________ 19

Supplemental supplies for industry________________-___-______ 26

Rural dependence on wells_________________-_-__--_--_______ 28

Ground water in the Piedmont-_________________________ 29

Ground water in the Coastal Plain______________________ 29

Waste disposal--__-___---___-__--___-_-_---___-----_--_,._- 32

Water quality..___________________________________________ 34

Effects of the geology._____--_-___-_-____-____-___-__-_ 35

Effects of man's activities__________________--_-----___- 37

Effects of storm-water runoff_________________-_-_-_--_-- 42

Effects of sedimentation._______________________________ 46

Recreation.._ _________________________________________________ 51

Looking ahead____________________________________________________ 53

Urban growth and zoning__.___._____-_____-_________-_-_-_____- 53

Population forecasts__-_____---____--_____-__-_____-------_---- 54

Projects and plans.___________.___________-__________-----_-_-- 57

Water for the metropolis from the Susquehanna River _ ________ 58

The Gunpowder Falls State Park_________________-___--_-_-_ 60

Zoning and related legislation________________-____----_---_- 62

Highways, byways, and a bridge. __ ___________-__--_-----__- 63

Suburbs and metrotowns__-______-__--____-_____-_-------_- 64

Reisterstown__ _ _______________________________________ 64

Carney-Perry Hall____-___________-_-_-________-__----_ 67

Towson-Cockeys ville. ________-_________--________---__- 67

Hereford-Belfast Road.________________________________ 67

Problems, choices, and compromises.__ _ ____________________-__-__-- 67

Living space versus water supply.___________-________-------____ 68

The potential sediment problem.--_-_____---____--___------- 68

An alternate metrotown site. _______________________________ 70

Water supply versus recreation.._____-_____________-_--------i-_ 75

Draft rates and water levels._____________________--_---_-_- 75

Augmenting the flow below Loch Raven Dam ________________ 79

Additional impoundments________-_______-._____-----_-_--- 79

Increasing the Patapsco water supply.___________-____------- 81

III
Problems, choices, and compromises Continued Page

Recreation versus living space_____--_---____-__-________-_____ 82

Publicly owned additional impoundments.___-__-____-----_-__ 83

Possibilities on the estuary________________________________ 84

Conclusions.__-_________-_---____-__--__-_--_-_-----______-_-_---_ 84

Selected references.________________________________________________ 88

Acknowledgments ______________________---_____-_----_--_---__-___ 90

Illustrations

Page

FIGURE 1. The three major uses of the Gunpowder Falls btfsin___-__ 2

2. Index map---_-__---_-_------_-_---____--__--_-_-_- 4

3. Map of basin population by election districts_____----__ 8

4. Graph of land used for farming in Baltimore County and

in the Gunpowder Falls basin._____________________ 9

5. Chart of precipitation record and probable rainfall

expectancies __.______-----_____-_--.__-_-____--__ 11

6. Graph of precipitation variability..--____._-________._ 12

7. Chart of average daily flow of Gunpowder Falls ________ 13

8. Graph of percentage of years when Gunpowder Falls

flow is less than average.__________________________ 14

9. Generalized geologic map of the basin and ground-water

zones ___________________________________________ 15

10-14. Graphs showing 

10. Range of low streamflows from zone !_________ 16

11. Range of low streamflows from zone 2_________ 17

12. The water-cycle budget, Gunpowder Falls basin _ _ 17

13. Calculated fluctuations in the ground-water

supply in a normal year__ ________________ 18

14. Water-level changes in Hydes well for 1961,

measured and calculated._---_____-_--_____ 19

15. Sketch of development of Gunpowder Falls a^ a water

supply ___________-----__-_------__--------__-__- 20

16. Graph of population and water used, 1910-63._________ 21

17. Map of water-service area (1964) and planned extensions._ 22

18. Graph showing probability of decreasing Liberty Reservoir contents_ _ _______________-_--___--__----___ 23

19. Graph of chance of failure of Gunpowder Falls watersupply system for various draft rates______________ 24

20. Chart of average daily flow of water over Lo?h Raven

Dam, 1953-62_______________-_____-_-_-______ 27

21. Map of the Coastal Plain section of the basin and the

Joppatowne well field.____________________________ 30

22. Chart of generalized logs of selected wells at Jopp^towne. _ 31 

23-25. Maps of 

23. Present (1964) and planned sewered areas______ 33

24. Reconnaissance surveys of Loch Raven Reservoir ___________________------_-_-_---_-__ 39

25. Reconnaissance survey of Prettyboy Reservoir __ 41 

26-28. Recorder charts of 

26. Runoff from area A__________-__--_-_--_--__ 43

27. Runoff from area B__________-----_-___---__ 44

28. Storm runoff from area A.__----___---------_ 46

IV
FIGURE 29-31. Graphs showing Page

29. Relationships of dissolved substances to rainfall

in area A__________._____________________ 47

30. Land use in the basin, 185<K2010_____________ 48

31. Sediment yield reflecting change in land use,

1850-1963______-_. _______________________ 49

32-35. Graphs showing population forecasts for 

32. Baltimore City_-_---------__-_--_-----_--_- 55

33. Baltimore County_________________________ 56

34. Metropolitan Baltimore____________________ 56

35. Gunpowder Falls basin._____________________ 57

36. Graph of water used by metropolitan Baltimore from

1900 to 1962 and projected to 2010. _ _ _ _ _ __ _ - _ _ _ 58

37. Map of present and proposed recreational areas ________ 61

38. Map of possible metrotown sites____________________ 65

39. Chart of capacity loss to sediment in small impoundments. ___-____________-_--_-_____--_-_____----_- 69

40. Chart of projected annual sediment yield as urbanization

increases ______________--__-___________-__------_ 70

41. Sketch map of Long Green Valley, a possible alternate

metrotown site._______----____-___________---_--_ 72

42-44. Graphs showing 

42. Low streamflow from Long Green Valley______. 73

43. Relations between draft rates and probability 

that Loch Raven Reservoir contents will fall 

below indicated amounts,._________________ 77

44. Amounts that draft rate can be increased witt

additional reservoir capacities______________ 80

45. Map showing possible route of pipeline that could be

built to divert water to Patapsco River basin. _______ 82

Tables Page 

TABLE 1. Water budget by months for the Gunpowder Falls basin, 1884-

1960__ _-_-- __- - _---------_--------.------ 13

2. Chemical analysis of water from selected streams in zone !__-_ 35

3. Chemical analysis of water from selected streams in zone 2_ _ _ _ 36

4. Water needed for Metropolitan Baltimore_____________-___- 59

5. Suitability or readiness of metrotown sites for urbanization-. 66
Gunpowder Falls, Maryland

USES OF A WATER RESOURCE TODAY AND TOMORROW

By Deric O'Bryan and Russell L McAvoy

Introduction

The Maryland watercourse known as Gunpowder Falls is a lovely 

landscape and a sustaining and relaxing environment a natural 

commodity for man to use and enjoy. The stream is not large, but 

as a water supply it is one of the most important in Maryland. More 

people depend on it for water than on any other water source within 

the State, and more money has been spent over a longer period to 

develop, treat, distribute, and protect its water than for any other 

Maryland stream. At 14 cents per thousand gallons, the water is one 

of the best bargains in Maryland, and a high-quality product, too, 

for the quality of Gunpowder Falls water is comparable with that 

of the best public supplies in the Nation. And it all belongs to 

Baltimore the Baltimore Bureau of Water Supply holds rights to 

all surface or runoff water in the entire Gunpowder Falls basin.

Different people value Gunpowder Falls in different ways. To 

each of the 1.4 million water users the proportionate capital value 

share of the Metropolitan Baltimore water system is about $160. 

Each of Maryland's taxpayers is contributing about $5 towards the 

acquisition of a State park in the basin; development and maintenance of that park will cost more on a continuing basis. Every one 

of the approximately 1,000 families who settle annually (the number 

increases each year) in the expanding suburbs and diminishing rural 

corners of the basin invests several to many thousands of dollars on 

a home. Additional tens of thousands of people think of Gunpowder 

Falls in conjunction with a fishing license, a boating fee, an available 

picnic table.

The present overall conditions in the Gunpowder Falls basin are 

good. Much has been written about the basin, planned for it, and
FIGURE 1. The three major uses of the Gunpowder Falls basin.

2
done to it. The basin now provides (1) pleasant living space within 

easy commuting distance from Baltimore for a rapidly expanding 

population, (2) an excellent water supply, and (3) countrysides and 

reservoirs for limited recreation (fig. 1). These are the three major 

uses of the basin which bear upon the water resources, now and in 

the foreseeable future.

To date the basin has served admirably; it has met most of the 

demands placed upon it. Present actions, trends and forecasts, and 

universal human desires clearly indicate that its land and water will 

be used to an ever greater extent. Wise planning and development, 

based on a sound understanding of the basin's potential, will permit 

further equitable exploitation. If demands exceed the area's ability 

to meet them, the consequences will include "water problems."

We have analyzed the Gunpowder Falls basin as it is today, with 

emphasis on its water resource. We have considered the trends and 

plans and probabilities in store for it, and have attempted to predict 

the local condition of the water resource in years to come. The crux 

of our report is: How does the Gunpowder Falls water serve now, 

and how well will it serve 50 years hence ?

WHAT THE BASIN PROVIDES TODAY 

Living Space

Room for homes living space is one of the three major uses of 

the Gunpowder Falls basin; it is probably the most rapidly increasing use because more and more of Baltimore's residents look for 

suburban or country homes. Where he lives is of primary interest to 

everyone. Accessibility to means of livelihood and a pleasing environment are basic considerations in the selection of a permanent 

address. The attractive basin, on the margin of a thriving metropolitan area, inevitably will contain more and more people.

Location

The Gunpowder Falls basin is almost entirely within Baltimore 

County, Md., and the stream drains slightly more than half of the 

county. The 350-square-mile watershed is about 50 miles long; the 

maximum width is about 16 miles (fig. 2). It starts in Pennsylvania, 

a few miles north of the village of Lineboro, Carroll County, Md. 

The rolling to rugged country of the headwaters approaches 900 feet 

in elevation. The stream enters the northwestern corner of Chesapeake Bay near the old port of Joppa, where the fresh flowing water 

is "lost to salt."
highway

r beltway 

highways

FIGURE 2. Index map, showing main roads and highways in the basin, existing 

and planned (adapted from Maryland State Roads Comm., Plan, and Programming Div., 1961). Shaded areas are communities and industrial parks now 

in existence.
History

Captain John Smith may have entered the Gunpowder River 

estuary in 1608 on his second voyage of exploration in the Chesapeake Bay. Later, other ships sailed up the Gunpowder River as far 

as they could, to the last cascade of the stream before it enters the 

Coastal Plain. Above this so-called Fall Line, the stream was named 

the Gunpowder Falls to distinguish it from the downstream ard tidal 

navigable part. The first white settlement in the region was established by 1627 southeast across the Bay on Kent Island, which is at 

the eastern end of the present Chesapeake Bay Bridge. The founder, 

Claiborne, soon after located a fur-trading station on Garrett Island 

(then called Palmer's Island) in the mouth of the Susquehanna 

River. Gunpowder Falls received its name about this time (Seitz, 

1946, p. 9) :

Tradition relates that the * * * Indians * * * when first they became acquainted with gunpowder * * * supposed it to be a vegetable seed. They sowed 

it and expected a good crop, unsuspecting that this seed would produce bloodshed and violence instead of flowers and vegetables.

"Old" Baltimore, on the Bush River about 10 miles southwest of 

the Susquehanna's mouth, became the recognized seat of government 

by 1674 for the then-extensive Baltimore County. The seat was 

transferred to Joppa, at the head of the Gunpowder River, nominally 

in 1707 and entirely by 1712. Government business and a pro-^Dering 

tobacco trade were conducted there until the county seat waf moved 

again in 1768 to present-day Baltimore. The Rumsey mansion 

(sketched on the cover), built in 1721, is the only surviving landmark 

of once-thriving Joppa.

Water has had an important role in the history of the Gun powder 

Falls basin since 1775, when William Hoffman built the first papermill in Maryland. He determined that (Seitz, 1946, p. 10, 11) :

The land surrounding the Great Gunpowder Falls contained much limestone 

which was considered favorable for water near by, since it kept the water 

clear and pure. This was very important for papermaking. All paper was 

made by hand; cloudy or muddy water would discolor the paper. The location 

which Hoffman chose was near the source of the river, which agair was an 

advantage, since upstream the water was clearer and would clear up quickly 

after heavy rains or flood. To be sure, it was a rather primitive wilderness 

around Gunpowder Falls, yet it was the abundance of water and its potential 

power that counted. Besides its natural features the place had some geographical advantages. Hoffman had been a papermaker in Pennsylvania. The new 

place was very close to the Pennsylvania-Maryland line, not more than sixteen 

miles from York.

* * * Time and place seemed to favor Hoffman's undertaking. The year 1776 

when he started to develop his business saw the beginning of the American 

Revolution. Shortly thereafter the Continental Congress moved frcm Philadelphia to York, Pennsylvania, a few miles north of Hoffman's mill.
According to Howard (1876, p. 818), Hoffman

* * * espoused the cause of the Colonies and greatly facilitated the Government by furnishing it with paper. When it adopted currency, he manufactured 

the paper for nearly all the Continental money; an important historical fact, 

not generally known * * *

Throughout the 19th century the basin invited the construction of 

more papermills and other industries dependent on good water. Iron 

smelters furnaces had their clay. Forests gave way to fields. The 

basin remained attractive, but many changes had taken place by 1881 

(Scharf, 1881, p. 15) :

The Great Gunpowder has all its large affluents within the limits of the 

county. Several of these, such as the Little Falls, Western Rrn, Black Rock 

Creek, and Beaver Dam, are powerful streams which drain mort, of the northwestern half of the territory. The river itself is one of marled beauty and 

variety, and especially so in its upper divisions. Like all the rivers and creeks 

of the uplands, it plunges at one place over huge rocks in a heavy cascade, at 

the next it forms strong rapids among the boulders, and then placidly glides 

along for nearly a mile in a wider, deeper channel, through a bed of alluvial 

soil. Its course is very sinuous, and particularly so, on a grander scale, south 

of the great fork below Whitehall; while farther down it becomes a majestic 

stream, full of energy, and supplying power for very large mills factories, and 

furnaces at many points along its course. Yet it no longer fills the wide 

channel which it once occupied, nor can it be estimated to contain much more 

than one-fourth the volume of water that belonged to it about one hundred 

years ago. The drying up of springs which originally supplied its tributaries, 

and the decomposition of the rocks into soils along the banks, have changed the 

order of distribution of the water and placed it in new relations. Hillsides, 

once covered with trees, shrubs, and herbage, retained the rain-water near the 

surface or allowed it to flow in a gradual supply to the springs beneath, while 

a notable proportion entered the cracks in the rocks to trickle through and 

converge in the streams at lower levels. But now the hillsides baked by the 

sun, allow the rains to run off by a single impulse, to be lost in swelling 

floods * * *

Careless use resulted in much erosion of the land in the 18th and 

19th centuries. The port of Joppa, once able to accommodate ships 

of 8-foot draft, became choked with sediments. The head of the 

Gunpowder River now is a tidal marsh (Gottschalk, 1945, p. 223- 

225):

A hydrographic chart of the Gunpowder estuary issued by the United States 

Coast and Geodetic Survey in 1846, a hundred years after the town (Joppa) 

had reached its peak of development, shows the above-tidewater delta surface 

to be a mile and a half long. By this date it had encroached within a quarter 

of a mile of the wharf. By 1897, when a second hydrographic chart was issued, 

the above-tidewater deposits had filled the entire estuary opposite the wharf 

and extended along a front three-fourths of a mile below the town. It was 

computed from data on these two charts that 7,900,000 cubic yar^s of sediment 

was deposited in the upper part of the Gunpowder estuary in the 51-year period 

between 1846 and 1S97.

6
Today the above-tide deposits extend nearly to the Pennsylvania Railroad 

bridge, a mile and a half below the townsite. The scene at Joppa Town is one 

of desolation. Old foundations are still visible through the tangled growth of 

weeds and underbrush. At a distance of 20 or 30 feet out from the original 

shore line is a heap of stones, the remnants of the old wharf. A hundred feet 

beyond is tree-covered land where ships once rode at anchor.

The countryside today is much less erodable than it was 100 years 

ago. A third of the land has been permitted to revert to forest, and 

many tilled fields have been converted to pasture lands. Agriculture 

and erosion resulting from it has been on the wane, at least since 

the turn of the century.

Seitz (1946, p. 53-54) brings the history of the basin up to date 

and provides a thoughtful appraisal of the increasing value of the 

water resources:

The new dam whose waters now cover the greater part of the old Hoffman 

land was named Prettyboy Branch, a small tributary of the Great Gunpowder 

Falls. Prettyboy Branch derived its name from a riding horse of the same 

name that belonged to a farmer through whose property the creek ran. When 

the horse met an untimely death by drowning in the little stream, the farmer 

commemorated Prettyboy by giving the creek the name of the horse * * *

It was the water that brought the Hoffman mills into existence. It was the 

water that attracted old William Hoffman to this part of the state when he 

came south in 1775. It was the water that let him choose the valley of the 

Great Gunpowder Falls for his industry. Now it was the water again that 

caused his land to submerge. In William Hoffman's time the water had driven 

the wheels and had served the men who owned the land. Five generations 

later, the water had become more valuable than the land, and the land with 

all its mills and buildings, its trees and groves, its charming memories and old 

traditions had to yield before the necessities of a new, hard, forward-pushing 

time.

Population

Most of the half million people in Baltimore County live close to 

or within the metropolitan area, but less than 20 percent live in the 

Gunpowder Falls basin, which occupies half of the county's total 

area. Three-fourths of the residents of the basin live near the 

northern boundary of the city of Baltimore, in an arc of expanding 

communities on the west and south sides of Loch Haven Reservoir 

and extending down the southern rim of the basin to tidewater. The 

rest of the Gunpowder Falls basin is still rural. The basin's approximate 1960 population is listed in the caption of figure 3, by election 

districts.

Economics

Agriculture is waning in the Gunpowder Falls basin as population 

and land values increase (Hamilton, 1961, p. 8) :

Suburbanization and industrial expansion, during the past 10 years, reduced 

by almost one-third the land in farms in Baltimore County. The number of
BASIty

10123 MILES

l.i i i i

 f

 ,-^ '^ ^ . "s< -. &% ( > -v^-^.^-^'

Beisterstown :^-

N

x '\ A

^?^,, ^iix,, \

T ^^9: ^^;%

BALTIMORE

FIGURE 3. Basin population, by election districts, based on the 1960 census 

(Maryland State Plan. Dept., 1961, p. 8-9; figures in parentheses in the following table show what part of the district is within the basin).

Area Population Population

Baltimore County:

District 4 (1/3) . _ . ___ 5, 200 

5 (all)________________ 2,550

6(all)___________ 1,625

7 (7/8)________________ 3,650

8 (4/5)______._________ 17,100

9 (l/3)-__________-____ 28,700

10 (3/4)_______________ 2,800

11 (4/5)_______________ 16,500

Total_______ 78, 125

Area 

Carroll County:

District 6 (1/2)______ 2,000

8 (1/4)________ 1,000

Harford County:

District 4 (few sq mi)___ 200

York County, Pa___ __ _ 2, 000 

Total__________ 5,200

Total for the basin (rounded) ______ ____________________________ 85, 000
farms declined by 51.7 percent. Baltimore County still ranks third in the 

number of farms, and the value of land and buildings per acre of $720 was the 

highest in the State.

Because of the heavy decline in the number of farms and land in farms, 

there was a corresponding drop in the acreage of all major crops and in the 

number of livestock * * *. The nearness to a large city and the heavy increase 

in housing projects has resulted in a good demand for nursery and greenhouse 

products.

The downtrend of farms and farming area from 1900 to 1960 is 

shown graphically in figure 4:

FIGURE 4. Graph of land used for farming in Baltimore County and in the 

Gunpowder Falls basin, 1900-60.

The farm obviously is giving way to the suburb, though at a diminishing rate as the distance from Baltimore increases. Data for 1945 

remind that a period of crisis, World War II in this case, can 

temporarily change a trend. In 1960, the land in the basin' was used 

as follows:

Use

Farmland- __________

Forest ______________

Urban and residentialReservoirs_ ________

Total (rounded).

Percent

58

28

12

2

Acres

130, 000

63, 000

28, 000

3,900

100 224,000
Small factories are along the railroad lines that follow the coast. 

A long-established metal-container-machinery plant and a metalparts finishing company are located on a tributary of Long Green 

Creek. A dozen or more enterprises are on Beaver Dam Run, 

between Timonium and Cockeysville; they include air-armament and 

electrical-equipment factories, a precision-tool shop, a veneer mill, a 

large and active limestone quarry. An extensive industrial park is 

growing west of Cockeysville. Many water-filled pits are evidence of 

past quarrying of Cockeysville Marble almost all the Washington 

Monument is faced with it.

The area contains no fuel resources and no minerals in quantities 

sufficient to warrant exploitation; it does provide building stone and 

crushed rock. Forests of the basin contain some trees of value, but 

lumbering of both hard and soft woods is sporadic; the borders of 

the two reservoirs are the only carefully planted and harvested forest 

tracts.

Roads

The Gunpowder Falls basin is crisscrossed more than 30 times by 

good, surfaced country roads, though the main stream valley, usually 

steep-sided and narrow, contains less than 5 miles of parallel roadways. A branch of the Pennsylvania Railroad winds up the central 

valley about 7 miles, from the head of Loch Raven Reservoir to the 

Little Falls tributary.

Several excellent highways traverse the basin. Interstate 83 (U.S. 

Ill) is the parkway between Baltimore and Harrisburg, Pa. The 

John Kennedy Memorial Highway and U.S. 40 connect Baltimore 

with Philadelphia and other cities to the northeast. The Baltimore 

Beltway cuts across the south-central part of the basin south of 

Loch Raven Reservoir.

Loch Raven Dam is 12 miles from Baltimore's Pennsylvania Station; 

Prettyboy Dam is 26 miles away; Joppatowne, near the mouth of 

Gunpowder Falls and the head of the Gunpowder River (or estuary) 

is about 18 miles northeast. The center of the basin is roughly 60 

miles from Washington and 80 miles from Philadelphia. The main 

roads and highways are shown on figure 2.

s

Water Resource

The Gunpowder Falls drainage basin and its landscape exist because of water action on land surface. The stream and its tributaries, 

in drought and in flood, have shaped the topography. Snow and rain 

have leached and weathered the surfaces of the bedrocks in varying 

degrees to form a smoothing and fertile cover of soil. The obvious

10
water resource is the river in the valley bottom. Wells and occasional springs indicate the not-so-obvious wealth of water in the 

ground.

Water, a Variable Commodity

The quantity of water in a basin such as the Gunpowder Falls is 

as variable as the weather, and the two are closely related because 

the source of all fresh water is precipitation. The average yearly 

rainfall on the basin is approximately 46 inches; its distribution is 

quite uniform. Records for the Baltimore area for the last 140 years 

(see fig. 5) show a recent low of 22 inches of precipitation in 1930 

and a high of 63 inches in 1889. The long record makes it possible

FIGURE 5. Precipitation record for 140 years and probable rainfall expectancies 

1817-1930, Baltimore, Md.; 1931-61, Towson, Md.

to determine about how often but not when a particular yearly 

precipitation value will occur. The additional ordinate scale at the 

right side of figure 5 shows that the drought of 1930 will be equaled 

or exceeded about once in a hundred years and that the high of 1889 

may also be expected about once in a century. Figure 6 indicates 

that 90 percent of the time in years (or 9 years in 10) the annual 

rainfall will be between 29 and 55 inches. Sixty percent of the time 

(6 years in 10) the annual rainfall will be between 34 and 47 inches. 

The yearly occurrence of precipitation has no apparent order; it 

varies randomly between extreme values.

784-926 O 66 2

11
20 50 80 

PERCENTAGE OF YEARS

95 99

FIGURE 6. Precipitation variability: Percentage of time when rainfall is more 

than the values shown in the left column. Example: 55 percent of the years 

have rainfall greater than 40 inches.

Precipitation also varies from month to month, the extremes being 

from 12 inches to less than 1 inch. These extremes usually occur 

during the summer and early fall. Average monthly precipitation 

records (water budget, table 1) for the period from 1884 to 1960 

show August to have the highest rainfall, 4.8 inches. The lowest rainfall, 3.3 inches, occurs during November and February.

About 60 percent, or 28 inches, of the yearly precipitation returns 

to the atmosphere as evaporation or transpiration. This water, lost 

insofar as water supply and recreational uses are concerned, is nevertheless the water upon which plantlife depends. Table 1 shows the 

evapotranspiration loss (the moisture which evaporates plus the moisture which is used by plants) to be quite small, about 5 percent, 

during the colder parts of the year, October to March, in comparison 

to the warmer periods when more water is transpired and evaporated 

than is precipitated in any one month (Munson, 1962). When evapotranspiration is low, the precipitation is about twice the runoff. 

Much of the snow and rain soaks into the ground to replenish the 

water supply depleted during the previous growing season. As the 

water table rises, more water drains to the watercourses. Thus, 

streams have higher flows in the winter than in the summer even 

though rainfall is less.

Each square mile of the basin yields an average of about 860,000 

gallons of water each day of the year, or about 1,360 gpd (gallons 

per day) for each acre. This yield varies from one-half of the 

average, or 450,000 gpd during a drought year, to about twice the 

average, or 1.4 mgd (million gallons per day) during a year of high

12
TABLE 1. Water budget, in inches by months, for the Gunpowder Falls basin

1884-1960

[Precipitation=Runoff+evapotranspiration±gain-loss]

Month

Feb.- 

April-. -.. .

July ..... ... .... 

Get __ . _ __ -_- -

Precipitation

3.6 

3.3 

3.8 

3.6 

3.9 

4.0 

4.5 

4.8 

4.0 

3.4 

3.3 

3.5

46

Runoff

1.7 

1.9 

2.2 

2.0 

1.8 

1.4 

1.3 

1.2 

1.0 

1.0 

1.1 

1.3

18

Evapotranspiration

0.3 

.5 

1.2 

2.1 

3.4 

4.2 

5.0 

4.4 

3.1 

1.9 

1.0 

.5

28

Change in ground water

Gain(+)

1.6 

.9 

.4

.5 

1.2 

1.7

Loss(-)

0.5 

1.3 

1.6 

1.8 

.8 

.1

0

runoff. These extreme values may be expected in 5 percent of the 

years or about 1 year in 20. The average daily flow of Gunpowder 

Falls from 1884 to 1960 is shown in figure 7; a comparison with the 

precipitation record in figure 5 shows the close relationship between 

the two. The average flow of the Gunpowder Falls at Loch Raven 

Dam, on the basis of the period of record from 1884 to 1960, is 264 

mgd. The values on the right side of figure 7 show how often ex-

-o

1900" 1910 1920 I93IT 'V94D- 1950 1960

FIGURE 7. Average daily flow and recurrence interval of Gunpowder Falls,

1884-1961.

13
treme conditions may occur. For example: the 1930 drought may 

be anticipated once in about 100 years.

The flow records of Loch Raven Reservoir between 1884 and 1960 

show that streamflow which is average (860,000 gpd per sq mi) or 

greater will occur only about 4 years out of 10, or 40 percent of the 

time in years. The flow for 6 of the 10 years will be less than this 

amount. These and other probabilities of varying yearly flows 

from the basin are illustrated in figure 8.

J700

70 60 50 40 30 20 

PERCENTAGE OF YEARS

10

FIGURE 8. Percentage of years when the flow of Gunpowder Falls is less than 

average. Example: About 60 percent of the years have streamflows less than 

the average yield of 860,000 gpd per sq mi.

Generally the flow of water in streams has a fairly uniform distribution except during low-flow periods. Then differences in geology 

become important, especially differences in the porosity of top soils 

and underlying rocks. The predominate rock formations in the basin 

occur in two distinct assemblages that delineate the two ground-water 

zones of the basin (fig. 9). The streams draining areas underlain by 

the weathered Cockeysville Marble (zone 2) have low flows markedly 

greater than those of streams draining areas of comparable size in zone 

1. The weathered marble has a greater unit storage capacity than 

other rocks. The water is accumulated during periods of high flow, 

and released to sustain flow during dry periods. The stream low flows 

for zones 1 and 2 are shown in figures 10 and 11, in million gallons per 

day per sq mi; variations in the water yielded to streams within each 

zone are shown as a range of values for a given percent of time.

Averages and Probabilities

The water-cycle budget for the basin, based on hydrologic records 

extending back to 1884 (table 1), is portrayed graphically in figure 12. 

The table shows the average precipitation each month and the yearly

14
..BASIN

PA_ 

HARFORD CO

1012 3 MILES

i.i I I i

H

?\

A

BALTIMORE

Zone 1

A, Wissahickon Formation 

B, Peters Creek Quartzite 

C, Baltimore Gneiss 

D, Gunpowder Granite 

E, Port Deposit Gneiss 

F, Gabbro 

G, Alluvium

Zone 8 

H, Cockeysville Marble

FIGURE 9. Generalized geologic map of the basin and ground-water zones.

average total of about 46 inches. Of this total, about 18 inches or about 

40 percent drains from the area, some as overland runoff and the 

remainder by infiltration into the ground where it flows downgradient 

to discharge into surface streams at lower elevations. About 6 inches

15
50 60 70 80 90 

PERCENTAGE OF DAYS

95 98 99

FIGURE 10. Range of low streamflows from zone 1.

a year is direct surface runoff, and about 12 inches drains through the 

ground (Dingman and Ferguson, 1956, p. 52). The remaining 28 

inches or 60 percent is lost through evapotranspiration. The runoff 

plus the evapotranspiration is equal to the precipitation received by 

the area on a yearly basis, but not on a monthly basis: From October 

through March the runoff plus evaporation is less than the precipitation ; from April through September the reverse is true. These excesses 

and deficiencies express the additions to or depletions from the groundwater supply for the basin (fig. 12). The fluctuations in ground-water 

supply in a normal year are illustrated in figure 13. Levels are highest 

in March. Then the evapotranspiration increases so rapidly as to intercept most precipitation before it has a chance to reach the water 

table. Only during extremely wet summer seasons does the groundwater zone become recharged by rainwater in excess of the loss 

through evaporation and transpiration. However, when water

16
40 50 60 70 80 90 

PERCENTAGE OF DAYS

95

FIGUKE 11. Range of low streamflows from zone 2.

JAN FEE MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

FIGURE 12. The water-cycle budget, Gunpowder Falls basin. Annual precipitation (46 in.) = evapotranspiration (28 in.)+runoff (18 in.).

17
JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

FIGURE 13. Fluctuations in ground-water supply in a normal year, calculated

from the water budget

is dispersed between soil particles, it will occupy a much greater area 

than when it is confined in a container such as a pail. In Long Green 

Valley, for example, which is an area of weathered Cockeysville 

Marble, the fluctuation in wells during a normal year is about 4 feet, 

that is, about 6 inches of water saturates about 4 feet of soil. During 

wet years, when precipitation contributes 8 to 10 inches of water to the 

water table, a fluctuation of about 5 to 6 feet may be expected. During 

drought periods the water table may drop as much as 8 feet. In the 

well at Hydes, near the center of Long Green Valley, the high and low 

water levels reflecting wet and dry periods since 1954 are 14.4 feet and 

21.9 feet below the land surface a variation of 7.5 feet. The actual 

monthly fluctuations of the water level of the Hydes well during 1961

18
21

JAN FEE MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

FIGTJBE 14. Water-level changes in Hydes well for 1961 compared with changes 

in water supply calculated from water budget.

are plotted in figure 14 against the predicted changes in water supply 

calculated according to values in table 1 and in figure 12.

Public Supply for Metropolitan Baltimore

About 100 years ago, consultants for the city of Baltimore recognized the potential of the Gunpowder Falls as a source of water supply. 

Practical damsites are seldom found at the mouths of rivers, and the 

Gunpowder Falls is no exception; only about six-sevenths, therefore.

19
of the total surface water available in the basin (from 303 of the 350 

square miles) was considered for water-supply use.

The first dam was built in 1881 about 1,000 feet downstream from 

the present Loch Raven Dam; it is still intact. The capacity of the first 

reservoir was about 500 million gallons. In 1914 the big dam at Loch

Prettyboy Reservoir

80 sq mi drained 

70 mgd average flow from drainage 

1500 acres of full reservoir water surface 

19,600 million gallons capacity (1953) 

520 ft above msl, elevation of dam crest

47 sq mi drained

41 mgd average flow.from drainage

Loch Raven Reservoir 

303 * sq mi drained 

194 mgd average flow from drainage 

70 mgd average flow from Prettyboy 

264 mgd average total flow 

2400 acres of full reservoir water surface 

23,700 million gallons capacity (1953) 

240 ft above msl, elevation of dam crest

FIGURE 15. Development of Gunpowder Falls as a water supply.

20
Raven was completed to a spillway height of 188 feet above mean sea 

level (msl). In 1923 the crest was raised to 240 feet to increase the 

capacity to 23.7 billion gallons. About 125 days of average flow, not 

considering drainage from the area above Prettyboy Dam, is required 

to fill Loch Raven Reservoir.

Prettyboy Dam, completed in 1932, created an additional 19.6 billion 

gallons of storage on the Gunpowder Falls. The drainage area above 

Prettyboy Dam is 80 square miles. About 280 days of average flow 

is required to fill the Prettyboy Reservoir. By the release of water 

through valves in the dam, this reservoir is used to maintain a high 

water level in Loch Raven Reservoir. Some reference figures for the 

developed water supply, as well as for the lower part of the basin, are 

given in figure 15.

The amount of water that can be taken from the Gunpowder Falls 

safely without exceeding the supply has been computed as 148 mgd 

(Gregory, Requardt, and Wolman, 1934, p. 81). This safe-yield estimate equals the capacities of the reservoirs minus 10 percent reserved 

for emergency purposes; it is based upon the 1930 drought period, 

which is considered the most severe on record. Figure 16 shows the 

amount of water used each year by Metropolitan Baltimore since 1910. 

Between 1881 and 1952, all the public water was supplied by the Gunpowder Falls. During this interval, the amount of water required for 

the peak year was 196 mgd in 1952 but from 1942 to 1956 the demand 

on the system exceeded the safe yield.

1,600,000

1,400,000

1,200,000

1,000,000

800,000

[ From Gunpowder Falls 

From the Patapsco River

400

300

200 5

100

600,000

1920 1940 1960

FIGURE 16. Water used and population in Metropolitan Baltimore, 1910-63.

21
In 1952, as an emergency measure, the city began pumping water 

from a temporary station at Avalon on the Patapsco River (fig. 2) 

while the dam for Liberty Reservoir was under construction. In 1955 

the first water from Liberty Reservoir was delivered to the metropolitan area.

Because of its elevation (the dam's crest is 420 feet above msl), 

Liberty Reservoir water is distributed by gravity flow to the Ashburton Filtration Plant (elevation 353 feet) and to most parts of the 

higher north and west sections of the metropolitan area (fig. IT). The 

water from Gunpowder Falls supplies the lower east and south sections. This redistribution in the supply system reduced the demand 

on the Gunpowder Falls water supply from a high of 196 mgd in 1952 

to about 104 mgd in 1958.

Planned

Existing- or under 

construction

FIGURE 17. Water-service area for northern Metropolitan Baltimore (1964) 

and planned extensions (Geyer, 1959).

22
In 1960 the City of Baltimore Bureau of Water Supply provided 

for a population of 1,386,500 living on 199 square miles composed of the 

entire city and adjoining parts of Anne Arundel, Howard, and Baltimore Counties (fig. 2). The average amount of water used was 202 

mgd; 250 million gallons was needed in a peak day.

The shifting of about one-half of the water-distribution system to 

the Liberty Reservoir Patapsco River source, plus a rapidly increasing 

demand for water in expanding suburbia, had raised the draft rate on 

the Liberty Reservoir to about 105 mgd by 1964, about the maximum 

that can be taken from this source.

The probability that water in a reservoir will reach any given level, 

regardless of the exact sequence of precipitation events, can be expressed by Langbein's (1958) theory of queues. A preliminary analysis of the effects of various draft rates on Liberty Reservoir, adapted 

from a more intensive study of the adjacent and similar Gunpowder 

Falls watershed, shows that, at the present rate of withdrawal, the 

reservoir may be emptied about 9 percent of the years or roughly once 

in 11 years (fig. 18). When increased percentages of the reservoir's 

content are withdrawn (noted on the left of fig. 18), the reservoir's 

water level is lowered accordingly (noted on the right margin). The 

computed safe yield of the reservoir, 95 mgd, would cause a deficiency 

in 2 percent of the years or about once in 50 years.

Water demand 

1963

410

405

399

393

383

70 80 90 100 110 

DRAFT RATE, IN MILLIONS OF GALLONS PER DAY

120

FIGURE 18. Probability, in percentage of years and with varying draft rates, 

of decreasing Liberty Reservoir contents below designated levels.

23
If the 1964 draft rate of 105 mgd is increased to 110 mgd, the reservoir may be expected to fail once in 5 years, or sometime in a year 

during 20 percent of the years; to increase draft another 6 million to 

about 116 mgd will cause it to fail on an average of once in 3 years. 

Consequently, further increases in the demand for public water for the 

metropolitan area will have to be met from the Gunpowder Falls until 

the projected Susquehanna River supplement becomes available. (See 

p. 58.) In all further computations, we assume that use of the Patapsco 

system will be stabilized at an average annual draft rate of 105 mgd.

Figure 19 shows the probabilities of Gunpowder Falls Reservoir 

failure calculated for various draft rates.

300

10 20 30 40 

PERCENTAGE OF CHANCE OF FAILURE

FIGUBE 19. Chance of failure of Gunpowder Falls water-supply system for 

various draft rates and years in which increased draft rates may be imposed.

24
A statistical analysis of the Gunpowder Falls water supply shows 

that the draft on it can be substantially increased. The computed safeyield figure of 148 mgd is quite conservative. A rate of 148 mgd would 

cause the system to be deficient about once in well over 100 years; in 

fact, the draft rate would have to be increased to about 175 mgd in 

order to anticipate a shortage once in a 100-year period. This computation does not mean that in every 100-year period there would be 

one year of shortage; it means only that, on the basis of the variability 

and quantity of past flows and the capacity of present impoundments, 

a shortage could be anticipated during 1 year in a 100-year period.

Draft rates higher than 148 mgd from Loch Raven Reservoir 

would cause deficiencies to occur at more frequent intervals:

Draft rate Probability of deficiency 

(mgd) Percent Year(s)

175__________________ 1 1 in 100

185__________________ 2 1 in 50

195__________________ 4 1 in 25

202__. _______________.___ 5 Iin20

218__________________ 10 1 in 10

240__________________ 20 1 in 5

257_._.____._.-__________ 30 Iin3

270.-.__.-__._._--._._.._ 40 2 in 5

The demand on Gunpowder Falls obviously can be increased considerably above the present rate of 110-115 mgd without much risk.

Prettyboy Reservoir has been full and overflowing since 1955, 

when it was drained to the bottom. This drawdown was during the 

moderately severe drought in 1954 when Gunpowder Falls streamflow 

was only 142 mgd and the demand on the system was 184 mgd; the 

Patapsco system had not then been completed. No releases were 

made from Prettyboy Reservoir until 1963, even though the flow of 

the Gunpowder Falls averaged only 139 mgd in 1959; the draft rate 

that year was 115 mgd and Loch Raven was able to meet the demand 

without water from Prettyboy.

The lowest level of the water surface in Loch Raven Reservoir in 

the last 23 years was about 6.5 feet below the dam crest; this level 

occurred in 1941 and again in 1955. The next lowest level was about 

5.5 feet in 1944 and 1959. The total area of the full reservoir is 

approximately 2,400 acres, and a drop in the reservoir level of 5-6 

feet exposes about 600 acres of shoreland, which is one-fourth of the 

surface area of the full reservoir.

25
Loch Raven Reservoir water levels will fluctuate more widely during 

years of low water demand, such as the present demand of 110 mgd, 

than during years when the demand is moderately high, about 175 to 

190 mgd. The water in Loch Raven Reservoir can be lowered 8 to 10 

feet below the dam crest and still supply the present demand by gravity 

flow. At high draft rates the level of the reservoir must be kept within 

the top foot of the pool in order to provide sufficient pressure to force 

the needed quantity of additional water through Montebello Tunnel 

to the Montebello Filtration Plant, if reliance is on gravity. Pumps 

have been installed to draw water below the 230-foot mark of the 

reservoir should the need ever be sufficiently critical to warrant the 

additional expense.

During the 6-year period from 1957 to 1962, the average flow of 

the river was 190 mgd, of which 115 mgd or 60 percent was diverted 

for metropolitan use. During the same period, Loch Raven Reservoir spilled in 51 of the 72 months or about 65 percent of the time 

in months. The amount of water spilled by the reservoir from 1953 

through 1962, the time of spills by months, and the months when no 

water spilled are shown in figure 20. During these 10 years the 

reservoir spilled some water during 60 percent of the months. The 

spills during the first 5 years were much less frequent than during 

the next 5 years, although the streamflow during the two 5-year 

sequences was comparable. The longest period of no spills was 14 

months.

Retentions of water by Loch Raven Reservoir lessens the flow 

below the dam during periods of little or no spill. On its way to the 

Fall Line, this part of the stream cuts through rugged Piedmont 

terrain in a channel that was designed by nature to accommodate an 

average flow of about 260 mgd. The present average flow is only about 

one-half that amount. Fifty percent of the days the flow is less than 6 

mgd, equivalent to a stream 10 feet wide, 1 foot deep, flowing with a 

velocity of 1 foot per second. Daily flows as low as one-fifth of this 

value (1.2 mgd) occur about 2 percent of the time.

Supplemental Supplies for Industry

During a peak period Metropolitan Baltimore needs as much as 

250 mgd, exclusive of industrial needs which alone are almost twice 

that amount. The huge Sparrows Point Plant of the Bethlehem 

Steel Corp. uses 400 mgd; other industries use about 50 mgd. Although few large industries are supplied directly by the metropolitan 

water system, Gunpowder Falls and Patapsco water are indirectly 

involved in a rather unusual way in the industrial use of water, as 

briefly described in the following paragraph.

26
Is

400

300

200

100

Streamflow.inmgd 

Draft rate, in mgd

a. _i to <

0

_

r

400

300

200

100

Streamflow.in mgd

Draft rate, i n mgd *: \ 109 J5SFIGURE 20. Average daily flow of water, by months, over Loch Raven Dam,

1953-62.

Water pumped from wells supplied as much as 50 mgd to industrial users in the years before World War II, an important contribution to the overall water supply at that time (1940) because the 

Bureau of Water Supply could not deliver more than 200 mgd and 

the average use was 161 mgd. Lack of pollution control and saltwater contamination as the result of over-pumping, however, is forcing a steadily increasing number of industries to buy water from the 

city's system. Only 100 wells remained in industrial use in 1958; 

they yielded about 24 mgd. Engineers at the Sparrows Point Plant 

worked out an equilibrium between continued use of water from 

wells, brackish water from Chesapeake Bay, and effluent from Balti784-926 O- 27
more's Back River Sewerage Treatment Plant in order to secure the 

supply of cooling liquid needed. In 1942 the company constructed, 

at its own expense, pipelines to convey the effluent from Baltimore's 

sewerage-treatment plant. In 1943 the company purchased about 

half the effluent available, 23.5 mgd, and it has continued to the 

present to use about half of the effluent available, even though the 

total amount has more than quadrupled. All parties are satisfied; 

the city is paid for its wraste water, and the company finds treated 

effluent less corrosive than brackish wrater.

Rural Dependence on Wells

For most residents of Metropolitan Baltimore, their only watersupply concern is the periodic nominal bill, but people living outside 

of the metropolitan area, north or east of the water-service area 

(fig. 17), are entirely dependent upon water from wells or springs, 

for the Baltimore Bureau of Water Supply holds the rights to all 

surface or runoff water in the Gunpowder Falls basin. Their water 

supplies cannot be secured directly from small impoundments, although such ponds are permissible for stock watering and for fishing, 

as is evident in the almost 500 ponds in the basin. The individual 

homeowner may use all the subsurface or ground wrater desired 

and available, but he must rely on wells or springs. Actually, all 

the water pumped from the wells in the basin totals no more than 

3 to 4 mgd. Furthermore, this use only interrupts the natural passage of the water to the stream; most" of the used water goes back 

into the ground via septic tanks.

About 40 percent of the precipitation on the basin becomes available as surface wrater and ground wrater (table 1). The amount of 

water in the ground may be estimated from measurements of annual 

precipitation and of runoff volumes, inasmuch as the water lost by 

runoff is replenished wdth more precipitation and recharge of the 

water table: the estimated ground-wrater runoff is 0.5 mgd per square 

mile (Dingman and Ferguson, 1956, p. 52), the approximate groundwater runoff from the 350-square-mile basin is 171 mgd, and ultimate 

practical recovery from this ground-water reservoir would be about 

one-third of the total (Otton, Martin and Durum, 1964, p. 96), about 

57 mgd. These gross figures mean that sufficient water might be 

pumped from the ground to supply 1,000 people per square mile at 

150 gpd per capita, or 1.500 people per square mile at 100 gpd per 

capita. This conclusion applies only to the hypothetical "average" 

square mile. Geology is an important factor in water availability 

and in well yields (p. 14); much more water may be expected from 

the sedimentary strata of the Coastal Plain, for instance, than from

28
the crystalline rocks of the Piedmont, and Cockeysville Marble 

formations yield the most water in the Piedmont.

Ground Water in the Piedmont

The surface or near-surface occurrences of the rock formations in 

the Gunpowder Falls basin are shown in figure 9. These contorted 

rocks form the rolling to rugged country the Piedmont and comprise all formations but the flat shoreland along Chesapeake Bay 

which is part of the Coastal Plain.

In the Piedmont, most of the available ground water is contained 

in the various "mantle" soils, seldom more than 100 feet thick, that 

overlie the bedrock, though some water is also found in the fractures 

in the bedrock. Some bedrock formations are more jointed and 

fractured than others, but fractures are not common at great depths. 

Cockeysville Marble is an exception; the undecomposed rock contains 

scattered solution channels capable of yielding moderate quantities of 

water to drilled wells; yields average 20 gpm (gallons per minute), 

and the maximum known yield in the basin from this formation is 

90 gpm.

Ground Water in the Coastal Plain

The Coastal Plain part of the Gunpowder Falls basin comprises 

less than 10 square miles between the Fall Line and Chesapeake 

Bay. We were able to estimate the ground-water supply expectancy 

of this area from well tests conducted at nearby Joppatowne. This 

residential development is within a mile of the southeastern boundary 

of the basin and within the Little Gunpowder Falls drainage; local 

geology, topography, and width of the Coastal Plain are almost 

identical in the two areas. The following evaluation of the groundwater resource at Joppatowne is highly indicative of the groundwater potential in the Coastal Plain part of the basin.

The Coastal Plain part of the Gunpowder Falls basin and the 

adjoining Joppatowne area are mapped in figure 21. The Joppatowne subdivision was started during the summer of 1962, and at 

completion will contain about 3,000 individual homes perhaps 10,000 

residents, plus churches, schools, and shopping and recreational 

facilities.

The geologic formations underlying the area consist of sand, silt, 

and clay beds 50-250 feet thick. These Coastal Plain sedimentary 

strata thin to the northwest and are not present northwest of U.S. 

Highway 40, which follows the Fall Line; they thicken as they 

extend to the southeast. Underneath these sand and gravel beds are 

the crystalline rocks characteristic of the Piedmont; because these

29
FIGURE 21. The Coastal Plain section of the Gunpowder Falls basin and the 

Joppatowne well field. (Line A-A' is line of wells and test borings shown in 

fig. 22.)

30
rocks store and transmit very little water, they are not considered in 

the estimate of the potential water yield.

A cross section along line A-A' of figure 21 shows the general 

nature of the deposits penetrated in the Joppatowne wells (fig. 22). 

Clean sand or gravel alternate irregularly with clay or sandy clay; 

the former are aquifers, strata producing water, and the latter are 

aquicludes, strata that yield little or no water. Individual deposits 

thicken or thin or pinch out entirely over a few tens or hundreds of 

feet. The pumping-test results indicate that most or all of the deep 

sand beds are connected with surface sand beds. The water table in 

the vicinity varies from about a foot to as much as 20 feet below land 

surface, depending on topography.

Though the strata both above and below the sand aquifers yield 

less water than the sand, they do transmit water to the sand when its 

water pressure is reduced by pumping. Hence, water in the sand 

aquifer may be replenished from one or both of two sources: (1) 

dewatering of the overlying clay and sandy clay, which in turn will 

be recharged by rainfall, and (2) recharge from streams or from the 

estuary when the water table is lowered sufficiently by pumping to 

cause water to flow from surface sources into the aquifer and toward 

the pumped wells. The ability of the aquifer to sustain large withdrawals over long periods of time will depend on these two sources.

100'

SEA 

LEVEL

100'

200'

| Clay, or

 sandy eiay,

fpSartd or'

j I sand 0r«d gravel

*j [i Observation 

11 well screen

ffliu

^00 FEET

FIGURE 22. Generalized logs of selected wells and test borings at Joppatowne, 

along line A-A' of figure 21. All wells are in the EC section of the standard 

location grid for Harford County, Md.

31
The following conclusions based on tests of the local ground-water 

supply for Joppatowne may be applied to the adjoining strip of 

Coastal Plain within the Gunpowder Falls basin:

1. The water-yielding characteristics of the aquifer at Joppatowne are comparable to those of aquifers in the Baltimore 

area.

2. The sand aquifer is replenished with water from adjoining 

strata as pumping proceeds. However, the data are insufficient to distinguish between water that comes from storage 

in the aquifer and water that may be derived from nearby 

streams and from the estuary.

3. The short-term pumping tests indicated that replenishment by 

local rainfall or stream infiltration is sufficient to sustain a 

continuous pumpage of 1.0 mgd or more from the sand 

aquifer. Some water pumped from the aquifer may be replenished with water from the estuary, and in late summer 

and early fall this estuarine water may become brackish. 

In the Baltimore area, similar formations were contaminated by brackish water as much as a mile inland from the 

nearest estuarine water (Bennett and Meyer, 1952, pi. 16). 

Salt-water infiltration could be detected by monitoring one 

or more observation wells situated near the estuary for 

increase in chloride content. Early warning of infiltration 

of brackish water into the aquifer should provide time for 

corrective procedures, because ground-water velocity usually 

is quite slow and decreases with distance from the center of 

pumping.

Waste Disposal

The inevitable companion of a water-supply system is a system or 

systems for the disposal of sanitary wastes and storm-water runoff 

whether for an isolated residence or for a metropolitan area. The 

basic problem is to keep the water supply clean and isolated from 

the wastes, particularly from untreated wastes.

Scattered rural homeowners have been able, and will continue, to 

get by with water wells and septic tanks. But these do not suffice 

when communities and suburbs expand beyond the 50-house unit 

figure which is defined in Maryland as the limit of a small subdivision (Geyer, 1959, p. 40) :

* * * It has been customary to require large lot sizes wherever septic tank 

systems are used. This may reduce the nuisance when the system fails but it 

will increase the per capita cost of sewers when they are built later on. It may 

also result in population densities that are much lower than are desirable for 

a given area.

32
The customary sequence of events for a householder on the fringe of 

a metropolitan area is first to pay for a septic tank and then to pay 

again, this time for sewer services.

Much thought is devoted to methods of waste disposal which will 

accommodate population growth and keep surface and ground waters 

reasonably clean. When population expansion results in contiguous 

communities, interceptors connect local sewerage networks to conduct 

wastes to large regional treatment plants. Figure 23 shows the 

present areas served by the metropolitan sewer systems, as well as 

extensions under construction or planned.

Proposed interceptor sewers 

(from Haney, 1962, fig. 6)

FIGURE 23. Present (1964) and planned sewered areas of northern Metropolitan 

Baltimore. (Adapted from Geyer, 1959, and from Haney, 1962.)

33
Metropolitan Baltimore's waste-disposal systems have kept pace 

reasonably well with its water-supply development (Geyer, 1959, 

p. 26):

* * * Unlike most other large cities, Baltimore has separate systems for 

collecting sanitary wastes and for collecting storm water runoff. This dual 

system makes it relatively easy to carry away and treat sanitary sewage while 

permitting storm runoff to discharge into natural water courses within the 

city. It avoids the periodic overflow, throughout the city, of mixtures of sanitary sewage and storm water. Such overflows inevitably accompany heavy 

rainfall, where a combined or single system of sewers is used to carry both 

storm water and sanitary wastes.

Runoff water is not comparable to raw sewage but it does contain 

pollutants. Streets and parking areas contribute snow-melting compounds, grease and gasoline, in addition to such trash as chewing 

gum, bits of tobacco, and rotting paper. Parks and lawns contribute 

insecticides and fertilizers; pets contribute wastes indiscriminately. 

Surface waters inevitably are degraded as urbanization takes place, 

as is discussed in the following section.

/ Water Quality

Water quality is determined basically by three major factors: 

geology, climate, and living organisms. The geology (and topography) governs the rate at which water moves over and through a 

mantle soil, the extent to which different minerals and different types 

of soils dissolve and the credibility of the different soils. The climate 

governs the amount of water available for solution and subsequent 

dilution of dissolved matter, the fragmentation of rocks and soils by 

freezing and thawing, and the movement of dissolved and suspended 

materials in the water.

Plants incorporate dissolved minerals into organic substances by 

utilizing them as food; when the plants die and decay, the minerals 

are returned to the earth. Bacteria, molds, and other minute organism aid in the breaking down of mineral matter to form organic 

substances during their life processes, and also in the reduction of 

organic matter to mineral matter. Larger plants protect the soil 

from erosion; their roots work into the earth at the same time, loosening the soil and dividing rocks and cohesive particles.

Many effects of man are obvious and well known, and no part of 

the Gunpowder Falls has escaped them. The early settlers were 

quite ruthless with the natural resources. At one time or another, 

practically the entire basin was "burned over" to provide "new" 

ground for farming. The soil was tilled until it could no longer 

produce acceptable harvests; then new areas were burned over and 

farmed, and the exhausted land was left to erode. Eventually a new

34
cover of trees and other vegetation would grow on the depleted soil, 

revive it, and then the farmers would move back again.

Today, happily, most of the basin is covered with forests c** welltended farms (see p. 9). The few industries release little waste; 

sources of industrial pollution now are less serious than in the heyday of the papermills in the 18th and 19th centuries. Present water 

quality reflects primarily the influences of geology, but some of the 

effects of the accelerated growth of local communities on water 

quality are becoming apparent (see p. 37).

Effects of the Geology

The chemical quality of the water reflects the soluble properties of 

the formations in the two generalized geologic areas. The firet, zone 

1 (fig. 9), is composed of schist, gneiss, and granite; it yields water 

that is soft and dilute and that contains comparatively little mineral 

matter, usually fewer than 65 parts to every million parts of water. 

The dominant minerals are calcium and bicarbonate. The highest 

concentrations occur during low-flow periods; lower concentrations 

result from dilution by rainfall and occur at higher flows. Chemical 

analyses for selected streams in the basin and the probable range of 

concentrations are presented in table 2.

TABLE 2. Chemical analysis of water from selected streams in zone 1 

[Concentrations in parts per million]

Substance

Magnesium _ . ______________

Sodium and potassium __________

Bicarbonate..- __________ .......

Sulfate.. _- _ _._._... ___-

Chloride __ ....... __ ................

Nitrate...................................

Detergent (ABS *). ............. . ......

1

12

2.4

3.9

36

40

5.7

63

.03

2

9.0

2.5

22

4.1

157

Sample

3

6.0

1.9

5.5

26

5.0

6.2

4.2

48

.06

4

6.5

5.4

2.1

22

3.6

8.9

6.3

58

.05

5

6.0

1.9

4.4

25

5.0

6.2

4.2

48

.06

Most 

probable

range

3-10

1-4

2-5

15-50

2-15

3-8

3-8

20-«5

1 Calculated.

2 Alkyl benzene sulfonate.

1. Gunpowder Falls at Lineboro, Md., Oct. 24,1962.

2. Gunpowder Falls at Lineboro, Md., Mar. 26,1963.

3. Little Falls at Blue Mount, Md., Oct. 24,1962.

4. Overshot Run near Sunnybrook, Md., Oct. 24,1962.

5. Lower East Fork Dulaney Valley Branch near Long Green, Md., Oct. 24,1962.

Zone 2 is composed of Cockeysville Marble, which weathers into 

fine loose particles. Marble consists of calcium carbonate and minor 

amounts of other minerals; it is more soluble than the rock formations of zone 1. Water draining from the marble can be quite hard, 

objectionable for some uses. For example, calcium carbonate pre35
cipitates and forms a scale on containers in which the wa ter is heated. 

Except for its hardness, the water of zone 2 is of excellent chemical 

quality. (See table 3.)

TABLE 3. Chemical analysis of water from selected streams in zone 2 

[Concentrations in parts per million]

Substance

Calcium. _____ .. ________ . _____________ .. _

Sodium and potassium

Bicarbonate-... __ _____ _. _______ . ______ ...

Sulfate ___ ____ . _____ ___ ____ .. ___ __ .__

Chloride.-.....---- _ .. __ .. .--_ _ ...... _ . .......... .......

Nitrate.......... ................................................

Detergent (ABS >). . .................... ......................

Sample

1

35 

15 

5.8 

122 

14 

25 

5.6

196

.03

2

45 

13

170

9.4

1204

Most 

probable 

range

30-60 

10-20 

2-8 

120-250 

2-10 

2-8 

2-10

120-250

1 Calculated.

2 Alkyl benzene sulfonate.

1. Beaver Dam Creek at CockeysvUle, Md., Oct. 24,1962.

2. Goodwin Run at Padonia, Rid., Mar. 26,1962.

Most of the streams in zone 2 have their headwaters in zone 1; the 

marble has weathered to form basins and valleys but the more resistant materials of zone 1 form the ridges and uplands. Consequently 

the water seeping from the hillsides reflects the chemical character of 

zone 1. The' water in the basin and valley streams actually is a mixture. The highest concentration of mineral matter in water of zone 

2 occurs during low-flow periods and is about 250 ppm (parts per 

million).

Except for Long Green Creek and some other small tributaries, 

surface water below Loch Raven Dam cannot be classified according 

to geologic locale because it flows across many different geologic formations characteristic of both zones (fig. 9). At tim^s the lower 

Gunpowder Falls receives most of its water directly from reservoir 

spill; at other times practically all its water comes from downstream 

ground-water seepage into the channel. This ground-water seepage 

locally contains calcium bicarbonate concentrations sufficiently high 

to make it moderately hard to hard.

The chemical quality of the water in the two reservoirs remains 

almost constant throughout the year because of their lar^e capacities 

in relation to inflow. Prettyboy Reservoir reflects the quality of zone 

1; there is no marble in the upper 80 square miles of the drainage. 

Chemical concentrations in Loch Raven are slightly higher than those 

in Prettyboy Reservoir because it receives water from both zones.

36
Total dissolved-mineral concentrations in Loch Raven rang*1, from 

70 to 100 ppm. The water is soft to slightly hard.

Effects of Man's Activities

At present, man's activities in the basin have only a slight effect 

on the chemical quality of the water. The Baltimore Bureau of 

Water Supply has done an excellent job of guarding the water's 

purity. However, a few man-caused factors are worth mentioning.

Analysis of water samples collected during low streamflow at eight 

scattered locations proved that detergents are present at many places 

in both ground and surface water, in concentrations rangirg from 

about 0.03 to 0.06 ppm. These concentrations are very lew, well 

below the foaming level. Ground water receives detergents primarily from septic tanks or similar disposal systems; streams' receive 

some in runoff from automobile-service stations, small laundnes, and 

dairy milking parlors and processing plants. Wells at some houses 

in developments in the basin have detergent concentrations high 

enough to produce quite a head of foam on a glass of wrier an 

indication of pollution from cesspools. The detergent concentration 

in Loch Raven Reservoir is about 0.03 ppm.

Nitrate and chloride concentrations are other possible indications of 

man's effect on the basin's water supply. Concentrations of nitrates 

much in excess of 5 ppm should be viewed with suspicion. Nitrates 

are a product of the final decomposition of organic matter, which is 

primarily protein in nature. A concentration as high as was found 

in sample 1 of table 2 indicates the breakdown of more than normal 

amounts of organic matter.

A concentration of chloride occurring naturally in water in a basin 

such as Gunpowder Falls probably will not exceed 10 ppm. Much of 

the chloride found in sample 1 of table 3 probably came frcm mancontributed wastes in or near Cockeysville. Chemical analysis of 

runoff in the urban areas of Baltimore County and city indicate that 

use of salt for melting snow and ice on roads may contribute 50 to 75 

ppm of chloride to the streams during winter and early spring.

With the assistance of personnel of the Baltimore Bureau cf Water 

Supply, reconnaissance surveys were made of Loch Raven Beservoir 

on June 5 and October 6, 1963, to note the effect of the Towson, 

Timonium, Texas, and Cockeysville populations on the quality of the 

reservoir water, as opposed to the contributions from the opposite or 

northeast side which is much more sparsely populated and little 

developed. Most observations in the tributary inlets to the reservoir 

were made within a few hundred yards of the stream inflowing from 

the contributing area. The first survey was planned to follow a rainstorm so that the observation at the sampling stations (see fig. 24)

37
would reflect a recent washing of the land surface. Heavy rains, 

totaling about 3 inches, fell on June 3 and 4.

Most of the reservoir inlets were turbid for a distance of onefourth to one-half mile. Observations were taken for temperature, 

dissolved-mineral concentrations, dissolved oxygen, and coliform bacteria (any of a number of bacilli that live in the intestines of vertebrates; the coliform count is used as a measure of the purity of 

water).

Dissolved solids were somewhat higher in samples from the Long 

Quarter Branch Cove of the reservoir (closest to Towson) than from 

the opposite side. This difference was explainable by the slightly 

different geologic terrain which contributes a harder type of water. 

One sample from a cove at station K had a much greater concentration than samples from any of the other stations, probably resulting 

from house-construction activities.

Farms and dairies are numerous to the northeast of Loch Raven 

Reservoir, especially in Dulaney Valley; higher counts of coliform 

bacteria might be expected in the adjoining water of the reservoir 

inasmuch as the bacteria live in the intestines of warm-blooded animals. Actually the reverse was true; the highest count ^as from the 

Long Quarter Branch arm. A fairly high count of coliform bacteria 

was expected and found in the headwaters of the reservoir because the 

drainage above is heavily farmed and the Beaver Dam Bun tributary 

contains <a large population in the towns of Timonium, Texas, and 

Cockeysville.

FIGURE 24 (opposite page). Map of reconnaissance surveys o* Loch Raven 

Reservoir, June 5 and October 6, 1963:

Station shown on fig. 24

A....................... ....

B._. ._.__...___.__ ______.

C ........................ -

D-. . ______ ......

B...... .......................

F... ........... .

G.. . .-___._

H -..-.___-__.._

I -.. __. ._ . .__

J-... ....... .

K..._. ..........

L_.-__-______.________

M......

N_ ...........

O --..__-____..______ . ...

P. -.-...

QR._ .

S__ ............ ..

Dissolved solids 

(ppm)

JuneS

48 

69 

71 

74 

76 

81 

81 

68

220 

160 

81 

93 

81 

93 

92 

87 

81

Oct. 6

68 

76

87 

88 

80 

87

83 

81

88

102

88 

90

Coliform bacteria 

count per liter

JuneS

70 000

95,000 

2,800 

13,000 

8,000 

12,000 

5,000 

10

11,000

60,000

54,000 

31,000 

8,000

Oct. 6

50 

100

350 

100 

200 

0 

50

0

0

50,000 

25,000 

500

D'ssolved-oxygen 

concentration, Oct. 6

Percent 

satu-ation

69 

60

59 

61 

55 

64

49 

69

61

69

Ppm

8.4 

7.4

7.5 

7.8 

7.0 

7.8

6.5

8.5

7.4

8.4

38
The low counts of coliform bacteria found at Dulaney Valley Eoad 

(2,800 per liter) and at Loch Raven Road (10 per liter) strongly 

indicate that the detention time of the water moving through the 

reservoir is sufficient to permit oxygenation of most of the bacterial 

load.

The fact that dissolved-oxygen concentrations in surface samples 

taken at all sampling stations had satisfactory saturation percentages 

indicates that oxygen-consuming organic pollution was not present 

in appreciable amounts. Some samples were highly saturated because

DULANEY VALLEY 

ROAD.BRIDGE

Dulaney 

Valley 

Branch

Long Quarter 

Branch

1 MILE

39
of the photosynthetic activity of oxygen-producing microvegetation 

such as algae.

The second survey of Loch Raven Reservoir, October 6, 1964, was 

made to determine reservoir conditions after a long drought. 

Streamflow was quite low, and rains sufficient to cause runoff had 

not occurred in many weeks. However, on the day of the survey it 

rained steadily and affected the results obtained at the sampling sites 

in Long Quarter Branch, Spring Branch, and Pot Spring Branch. 

The colif orm concentrations were fairly low at all other sampling 

stations (fig. 24). The influent streams to Loch Raven appear to 

carry relatively low counts of coliform bacteria during low-flow 

periods, and the major counts of coliforms are washed into the lake 

during times when rainfall is sufficient to produce surface runoff. 

The second survey confirmed the ability of the lake to assimilate 

bacteria; the counts of colif orms were again low at the bridges on 

Dulaney Valley and Loch Raven Roads, as well as at the midpoint 

between the dam and Loch Raven Road.

The dissolved-oxygen concentrations in samples taken about 3 feet 

below the surface ranged from 6.5 to 8.5 ppm. These concentrations 

are about two-thirds that of water saturated with oxygen.

Dissolved-solids concentrations averaged about 85 ppm and were 

about 10 percent higher than during the June 5 survey. The dissolved solids in Long Quarter Branch Cove were appreciably higher, 

probably from effluents from the shopping center in that small 

drainage basin.

Prettyboy Reservoir was surveyed on October 5, 1963, and results 

are shown on figure 25. The flow of streams into the reservoir was 

very low. The data indicate that Prettyboy has higher colifonn 

bacteria counts, lower dissolved-solids concentrations, and highei 

dissolved-oxygen values than Loch Raven Reservoir.

FIGURE 25 (opposite page). Map of reconnaissance survey of Prettyboy Reservoir, October 5, 1963:

Station shown on fig. 25

A.. _ ___-.____- ..______-.__________--.__ _ _

B. ....... ........ ........... ..... _ .... ... ._ .

C. -.- .--.... . -... . 

D

E

F __ _ _ . .. _

G

H - _ ............ ... . ............

I

J_ - - _- . . --.--.-. ... ...

Dissolved 

solids 

(ppm)

45 

48 

42 

47 

46 

47 

48 

47 

42 

45

Colifonn 

bacteria 

count per 

liter

5,000 

1,400 

2,500 

1,000 

2,000 

7,000 

1,800 

4,000 

2,800 

4,000

Dissolved-oxygen 

concentration

Percent 

saturation

77 

74 

61 

75 

73 

82 

73 

77 

72 

77

Ppm

8.5 

7.4 

7.8 

7.0 

7.7 

7.7 

7.3 

8.5 

8.5 

9.0

40
For these surveys, all samples were taken at the midpoint across 

the channel where the water shallowed to 5 feet. The coves in 

Prettyboy Reservoir are narrow and deep, and there samples can be 

obtained quite close to the influent streams; however, the shallow, 

broad silt-filled coves of Loch Raven Reservoir did not permit 

sampling close to the influent streams. This difference in depth, 

together with the fact that water remains longer in Loch Raven, 

explains, in part, the higher coliform counts in Prettyboy Reservoir. 

There is, however, strong indication that streams influent to Prettyboy 

Reservoir carry higher counts of coliforms at low flow than do the 

streams flowing into Loch Raven, that is, that more polluting sub1 MILE

f

ROAD
stances are being introduced directly to the streams in the Prettyboy 

area. The surface area of Loch Raven Reservoir is 50 percent 

greater than Prettyboy Reservoir; hence the chance for oxygenation 

of its water is greater by that amount.

Effects of Storm-Water Runoff

When rain falls, part of it soon enters the watercourses as stormwater runoff. This runoff usually brings with it a myriad of things 

 dissolved chemicals, bits of trash, oils and tars from roads, decaying organic matter, and so on that acculumate in the watercourses 

and decrease the purity of the water in the drainage basin. To determine about how much contamination the runoff from the planned 

urbanized areas will add to the Gunpowder Falls basin, two areas in 

the City of Baltimore were selected for study. Although these areas 

are outside the basin, they were chosen because their hydrological 

environments are like those of the urbanized areas that are now 

growing in the basin.

Area A is a 100-percent residential section containing detached and 

semidetached homes on lots of about 2,000 to 3,000 square feet; it has 

been developed within the last 10 years. The total area is 47 acres, 

and 44 percent of it is covered with impervious surfaces such as 

streets, sidewalks, and roofs. It has a population of about 1,600 

people. Sanitary sewers carry all domestic sewage from the area, 

and storm sewers carry away excess water from rain, lawn-sprinkler 

runoff, automobile wash water, and the like. The storm sewer discharges into a tributary of Herring Run.

Area B is a mixed residential area containing row houses and a 

highly developed shopping center. Sixty-eight percent of its total 

area of 47.4 acres is imperviously surfaced. The residential area 

contains about 800 people. The shopping center occupies about 17 

acres and consists of a large department store, two supermarkets, one 

theatre, and about 25 smaller businesses. Area B has separate sewer 

systems for sanitary wastes and for storm runoff. The storm water 

also drains into a small tributary of Herring Run.

Areas A and B are almost identical in size, shape, and slope of the 

land surface; they are part of the same drainage basin, were developed at the same time, and are about 1 mile apart. Consequently, 

any difference in the quality of the water draining from the areas 

must be due to differences in man's activities. Figure 26 is a record 

of the amount of dissolved mineral matter contained in the water 

draining from area A for a 4-day period. Little change in water 

'quality takes place from 8:00 p.m. to 8:00 a.m., but from 8:00 a.m. 

to 8:00 p.m. the changes are frequent and extensive. These changes

42
tor

Noon

FIGURE 26. Recorder chart of runoff record from area A for a 4-day period. 

The continuous record lines show conductivity values; dissolved-solids concentrations are approximately 60 percent of the conductivity values.

are directly attributable to the dumping and flushing of liquid and 

other wastes into the storm sewers. Some of the larger flushings of 

polluted water, such as the one between 11:00 a.m. and noon, are due 

to street washes. The smooth record obtained at night shows that the 

normal mineralization of water in the area is about 100 to 110 ppm; 

because of the indiscriminate dumping, flushing, washing, and watering that takes place during the daytime, however, the mineralization 

of water fluctuates from about 110 ppm to more than 500 ppm of dissolved solids. This diurnal change was observed over a 2-month 

period.

During the warmer weather in April and May, the small stream 

channel which received the water from the storm sewer of area A had 

a luxuriant growth of algae, slimes, and molds which were quite

784-926 O 66 * JQ
odoriferous. The nitrates (10-15 ppm) and phosphates (2-3 ppm) in 

the water were nutrients for the streambed growth.

During and after storms, high runoff scours these organisms from 

the streambed and washes them to a settling area, in this case the 

Back River. Oxidation of these materials uses the oxygen in the 

water and can result in an environment which will not support 

aquatic life. Such water in a settling area can create taste and odor 

problems, and even health hazards, and it is generally unfit from an 

aesthetic point of view.

The record of the dissolved-mineral matter in water draining from 

area B (fig. 27) is much more uniform than that from area A. The 

small increases (caused by increase of calcium chloride) which occur 

hourly are of undetermined origin; they may be caused by automatic

** «

Noon

FIGURE 27. Recorder chart of runoff record from area B, 11 a.m. to 5 a.m. 

The continuous record line shows conductivity values; dissolved-solids concentrations are approximately 60 percent of the conductivity values.

44
defrosting refrigeration equipment used by the large supermarkets. 

Several large increases in dissolved solids occurred during the day. 

A single gasoline station was the main source of pollutants from 

area B; it contributed foamy car washings, gasoline, motor oils, 

greases, and radiator flushings.

The stream channel below the storm-sewer outfall of area B did not 

have as much algae and slime as area A, probably because of the inhibiting effect of the petroleum products in the runoff. Observed nitrate, 

phosphate, and chloride concentrations were as much as 4, 10, and 

80 ppm, respectively. Besides dissolved materials in the water, both 

areas contributed notable quantities of newspapers, cardboard boxes, 

tin cans, rags, broken glass, sand and gravel, wire, children's toys, and 

so on, to the storm drains.

During low flow, colif orm bacteria counts were quite low, generally 

less than 100 per liter. It is doubtful that storm runoff in area B 

would have as high a coliform bacteria count as the water in most 

arms of Loch Raven Reservoir because the high density of the development and the local laws tend to keep to a minimum the number 

of animals in such an area.

During periods of no precipitation, or runoff due only to melting 

snow and ice, the flow from the area was only a fraction of that 

occurring during a storm. The late winter and early spring runoff 

was about 25 to 40 gpm. In April and May, when evapotranspiration demands increased considerably, the flow diminished to 5 to 10 

gpm.

Runoff from both areas was quite rapid during a storm. Within 

a few minutes after a rain began, the flow increased noticeably and 

then varied almost as the rainfall. Within 30 to 60 minutes after a 

storm the flow was almost back to the prestorm amount.

Runoff from the storm of April 29-30, 1963, from area A was 

analyzed to determine the amount of dissolved matter. Figures 28 

and 29 show the sequence of events for this storm. Rain began to fall 

at 6:00 p.m. on April 29; during the next 10 hours about 1 million 

gallons of water fell on the area of which an estimated 450,000 

gallons ran off. The 5 weeks preceding April 29 and 30 were very 

dry and consequently runoff from pervious areas was negligible, the 

runoff coming primarily from the impervious surfaces which constitute 44 percent of area A. The calculated amount of dissolvedmineral matter in the runoff resulting from man-made causes was 

about 350 pounds; the average concentrations for the storm water 

was about 95 ppm. This concentration can be interpreted to mean 

(1) that the impervious surfaces resulting from urbanization permit

45
Vi8i.up.iw

Noon

FIGURE 28. Recorder chart of storm-runoff record from area A, Apr. 29-30, 1963. 

The continuous record line shows conductivity values; dissolved-solids concentrations are approximately 60 percent of the conductivity values.

a 40 to 50 percent greater runoff and (2) that the amounts of dissolved solids are 30 to 50 percent greater because of urbanization.

Effects of Sedimentation

The Gunpowder Falls basin has long been a notoriuos producer of 

sediment. The area was heavily farmed during the 18th and 19th 

centuries. Where forests were not burned to make way for fields, 

they were cut heavily to feed papermills and satisfy lumber needs. 

The harbor of old Joppa was used only about 100 years before 

it became choked with silt (see p. 6). The first municipal watersupply reservoir in the basin, built in 1881, lost 85 percent of its capacity to sediment by 1900. Only by the dredging of 1.8 million tons

46
6:00 p.m. Midnight 6:00 a.m. Noon 6:00 p.m.

FIGURE 29. Relationships of dissolved substances to rainfall in area A during 

the storm, April 29-30, 1963.

of sediment was it made to last until the present larger Loch Raven 

Dam was constructed in 1914.

Land use is the dominant factor in sediment production within the 

basin, geology and climate playing lesser roles. Land use at the 

present time is about 60 percent farm and pasture, 30 percent forest, 

and 10 percent urban or suburban (see p. 9). The basin has 

changed a great deal since the coming of the white man more than 

300 years ago. Before the advent of Europeans, forests almost certainly covered at least 80 percent of the area, the remainder being 

forest-fire glades and small fields tilled by Indians, but by 1900 an 

overwhelming 90 percent of the land was in farms (fig. 30).

The usual sequence of erosion and sedimentation has been summarized by Guy and Ferguson (1962, p. 27) :

Sediment derived from natural and agricultural erosion has always given 

varying degrees of concern to those who plan, finance, or manage water reservoirs. A third source of sediment threatens to reduce further the useful life

47
1850 1900 1950 2000

FIGURE 30. Land use in the basin, 1850-2010. Gray area shows the most probable ranges of values for periods for which records are incomplete and for the 

forecasts.

of many reservoirs downstream from urban centers. This newly recognized 

source is the result of the increasing quantity of soil material exposed or 

reshaped by modern earth moving equipment during the construction phases of 

urban development. The inevitable widening of stream channels after urbanization is an additional source of sediment.

Sediment yield from forested land is quite small, averaging about 

50 tons per square mile per year from a basin such as the Gunpowder 

Falls. Before the area was settled, the 350 square miles of the 

basin probably yielded about 15,000 to 20,000 tons per year to the 

Gunpowder River estuary.

Agricultural use of land accelerates erosion because the land must 

be ploughed and broken up before planting. While the earth is 

loosened and exposed, rainfall and runoff carry away some of the topsoil. Then, as the sediment-carrying waters enter lakes and estuaries 

downstream, the topsoil is redeposited. Row crops, such as corn, 

permit more erosion than cover crops, such as clover, because a large 

percentage of the soil surface in a field of corn remains bare throughout the growing season. Obviously, it is difficult to estimate annual 

erosion from an "average" square mile of farmland in the Piedmont.

Gottschalk (1945, p. 224) determined that about 6.5 million tons 

of sediment was deposited in the upper part of the Gunpowder 

River estuary between 1846 and 1897, assuming that no sediment 

was lost to the lower part of the estuary or to the Chesapeake Bay. 

This total resulted from about 340 tons per square mile per year, as

48
shown in the lower left block of figure 31. During the last 20 years of 

this period, the original Loch Raven Reservoir was intercepting about 

30 percent of the sediment from the basin. If allowances are made 

for this interception and it is estimated that the 340 tons per square 

mile per year deposited in the estuary constitute 40 to 50 percent of 

the total yield per year for the 1846-97 period, the annual yield 

appears to have been about 900 to 1,100 tons per square mile per year.

From 1881 to 1900, the original Loch Raven Reservoir trapped 

about 2.5 million tons of sediment. The reservoir caught 25 to 35 

percent of the sediment inflow; consequently, the basin's yield probably was within the range of 1,000 to 1,200 tons per square mile per 

year. (See fig. 31.) At that time the basin was 90 percent farmed 

(fig. 30), and farming practices generally were not in keeping with 

soil conservation.

The 1943 survey of Loch Raven Reservoir (Gottschalk, 1943, p. 

16-17) showed that the sediment yield per square mile was 800 tons 

per year for the preceding 29-year period. This yield totaled 7.9 

million tons and reduced the capacity of the impoundment about 8 

percent. A survey of Prettyboy Reservoir the same year revealed 

that it had accumulated about three-fourths of a million tons of 

sediment during its 11-year span, or about 900 tons per square mile

1850 1900 1950 2000

FIGURE 31. Sediment yield reflecting change in land use, 1850-1963. (For 

a fuller explanation, see p. 51.)

49
per year. These sediment yields are shown as the center block 

of figure 31.

Analysis of Loch Raven Reservoir survey data (Holeman, written 

commun., 1963) for the Dulaney Valley and Long Quarter Branch 

arms indicate that the average annual yield of sediment for the 1914- 

62 period was about 3,000 and 1,300 tons per square mile, respectively, 

from those tributaries. The estimated yield from Dulaney Valley 

Branch may be too high, although about 60 to 70 percent of the drainage was intensively farmed during the period. Much of the Long 

Quarter Branch drainage was farmed prior to World War II; since 

then, fields have been replaced by residential developments.

Surveys of both reservoirs in 1961 (Holeman, written commun., 

1963) showed that the sediment yield had declined markedly. For 

the 1943-61 period, the yield of Loch Raven Reservoir was only 233 

tons per square mile per year, almost 70 percent less than the 800- 

ton figure of the earlier survey. The drop in yield is attributed to 

the decline in the amount of land farmed and to conservation practices. At the present rate of sedimentation, Loch Raven Reservoir is 

expected to last well over 1,000 years. The yield to Prettyboy Reservoir remained fairly high at 550 tons per square mile per year for 

the 1943-61 period, about 40 percent less than the 900-ton figure 

estimated from the earlier survey. This reservoir also appears to 

have a life expectancy of more than 1,000 years. The estimated 

annual sediment yield per square mile of the Gunpowder Falls basin 

for the past 100 years is shown by the curve in figure 31.

Erosion resulting from urban growth is now recognized as a serious 

problem. After a strip of agricultural or wooded land is earmarked 

for a residence, an industrial park, or an expressway, bulldozers, 

earth scoops, and graders remove the cover of vegetation. The earth 

is thus exposed, in cuts and fills, to rain and storm runoff. Weathering and erosion of the soil continue throughout the period of construction until the ground is again covered with grass and other 

plants or sealed with impervious roofs and pavements. A house plot 

may be stripped, the home built, and the yard replanted all in a few 

months but sections of an industrial park, a superhighway, even of 

a large residential development may remain bare for several years.

Holeman and Geiger (1959) made a sedimentation resurvey of 

Lake Barcroft, Fairfax County, Va., to determine the change after 

two-thirds of the watershed had been urbanized. Guy and Ferguson 

(1962, p. 30) concluded from the Lake Barcroft resurvey:

* * * that each square mile passing through the construction cycle processes 

of clearing, grading, building, and seeding results in an accumulation of approximately * * * 25,000 tons of sediment per square mile.

50
The similarities between the Lake Barcroft and Loch Raven areas 

include geology, topography, climate, and the complexity of construction methods; therefore the sedimentation estimate of 25,000 tons per 

square mile for the period of development for Lake Barcroft probably 

is applicable to sections of Gunpowder Falls slated for urbanization.

Sediment yield from an urbanized area, after construction is completed, is 50 to 100 tons per square mile per year, or about one-third 

of the present yield of the Gunpowder Falls basin excluding the part 

above Prettyboy Reservoir where the yield is about 550 tons per 

square mile per year.

A major source of sediment from an urban area is the ero^on of 

stream channels. Storm water leaves an urban area in greate^ quantities and at faster rates than from "natural" or rural lands. The 

impervious surfaces of a city do not permit the water to so^k into 

the ground; instead it is routed into gutters, lined ditches, and 

sewer pipes. Carter (1961, p. 9) found that the maximum flood discharge expected in a 2-year period is about twice as great from a 

suburb as from a countryside. This additional flow has increased 

energy which results in the rapid widening and downcutting c f channels to undermine retaining walls, bridge abutments, and cnlverts, 

until the stream bed is sufficiently enlarged to accommodate the 

excess water. Thus, man-made earthfills may be washed away, 

and streamside structures are threatened or destroyed.

In summary, the sediment yields that can be expected from the 

basin according to the use of the land are:

Tons per square m'le 

per year

Forested land---_-_---_-___..___-_____-__-_-__ About 50

Farmland______..___.____..___._.____._____ 1,000 to 5,000

Land stripped for construction. ________________ 25,000 to 50,000

Urban and suburban land. --_-____-_________-- 50 to 100

Recreation

The influence of an expanding metropolis and its inhabitants on 

adjoining green spaces, watersheds, and countrysides suitable for 

recreational purposes is an increasingly important problem.

In August, 1958, a working committee of the Baltimore Regional 

Planning Council recommended that 10 acres of State or regional 

park land and 33 acres of open spaces should be available p^r 1,000 

people for recreational purposes. The committee noted that watersupply reservoirs had a maximum permissible recreational u?e below 

that of reservoirs for which the maintenance of water quality was not 

of first importance. The committee determined a 1958 deficiency of 

about 30 percent in local recreational areas, and it forecast a 58-

51
percent deficiency by 1980 if no new areas are acquired. This conclusion was the impetus for the present acquisition of land for the Gunpowder Falls State Park (Alien, 1958, p. 3).

Much of the Gunpowder Falls basin possesses attractive open 

spaces: forests interspersed with fields and pastures, a rolling to 

rugged topography, and a generally clear stream. Many stretches of 

valley remain sparsely settled and well timbered by second-growth 

trees. Most of the valley is inaccessible by car, but roads border 

and, in places, cross it.

The City of Baltimore Bureau of Water Supply owns and controls 

the Prettyboy and Loch Kaven Keservoirs and the acreages around 

them. The diligent and careful supervision of these areas is aimed 

at maintaining the high quality of the water and keeping the watershed clean, but the reservoirs are open to the public. The pleasing 

waterscapes and stalwart dams are photogenic and aesthetically satisfying in themselves. Well-tended forests encircle the shores, and 

they have provided the city with about a million dollars worth of 

lumber more than half a million from November 1955 through 

June 1959 (Keigner and Sushko, 1960, p. 3) from controlled 

logging around Loch Kaven. This planting and thinning has improved the appearance of the area and resulted in healthier trees. 

Thus, areas set aside for conservation or recreation may provide 

additional uses.

The following recreational pursuits are permitted at both reservoirs :

1. Fishing from designated shores and from boats equipped with 

electric motors in waters a mile or more above the dams. 

The boat center at Loch Raven Reservoir is exceptionally 

well equipped and maintained.

2. Picnicking in prescribed areas; about 200 rustic tables have 

been installed at Loch Raven Reservoir and 75 at Prettyboy 

Reservoir. More are being added each year.

3. Horseback riding and hiking on well-maintained logging 

tracks and trails.

4. Miscellaneous activities. Additional attractions at Loch Raven 

are a clubhouse, golf course, and skeet range. Deer hunting 

with bow and arrow in season is allowed si Prettyboy 

Reservoir.

Some of the specific prohibitions are:

1. No wading, swimming, sailing, or canoeing.

2. No cottages may be constructed, nor is camping condoned.

3. No fires may be built, even in the picnic areas.

52
4. No fuel-powered motorboats (other than official patrol) are 

allowed on the lakes.

Approximately 200,000 people annually fish the lake and stream 

waters; many times that number frequent the dams to gaze at the 

lolling carp and schools of bluegill. The stream above Loch Raven 

is stocked with trout. In the spring, runs of salt water fish svim up 

the channel as far as Loch Raven Dam; Gunpowder Falls hr.s been 

listed as one of the eight best shad streams on the Atlantic Coast.

Other recreational facilities in the basin include:

1. The Valley Ranch near Roller, Carroll County, which keeps a 

stable of horses and is a convenient headquarters for fishing 

and hiking parties.

2. The Gunpowder Youth Camps, Inc. Puhtok Boys Camp and 

Alkor in the valley east of Hereford.

3. The 100-acre Cone Boy Scout Reservation, between th?< confluence of Long Green Creek and Gunpowder Falls, which 

is used for camping and other scouting activities.

4. The Gunpowder Rifle Range, one-half mile north of Notchcliff Road, which is used periodically by the Maryland 

National Guard for high-caliber rifle practice (it will be 

discontinued when the State park is opened).

5. An area reserved for winter sports ice-skating, sledding, skiing near the old County Alms House east of Texas.

6. Several restaurants, periodically attended by civic groups 

from the Baltimore area, tourists, and local residents.

7. Several private clubs.

The Gunpowder Falls basin has the requisite attractions fo^ many 

recreational uses which involve the natural and developed parts of 

the water resource. Adjacency to Metropolitan Baltimore has resulted in the many recreational facilities now available. Mere will 

be needed to satisfy increasing pressure from those seeking pleasure 

and relaxation. Satisfaction of this need, with minimal effect on the 

important water supply, is considered in the following section on 

"Water Supply versus Recreation."

LOOKING AHEAD 

Urban Growth and Zoning

The word "megalopolis" is self-explanatory, if you can imagine a 

city composed of cities. Jean Gottman popularized the term in a 

provocative article (1957, p. 189-200) considering the urbanization 

of the northeastern seaboard. He envisioned megalopolis as an urban

53
colossus reaching from Boston to Richmond. The Gunpowder Falls 

is within this area.

Growth by urban sprawl is being criticized more ard more, and 

zoning planning for the future is the order of the day. Planning 

"wedges and corridors," (open spaces between strips reserved for 

tomorrow's industrial and residential growth) and "naetrotowns," 

(peripheral cities of the future, each to accommodate one to two 

hundred thousand people) is a publicized pursuit, although some of 

the specific forecasts and recommendations apparently are debatable, 

impractical, and even unacceptable, in whole or in part, to many 

groups.

The Gunpowder Falls basin today is a focus of attention for zoning 

and planning. Part of it is being acquired for a State park by the 

Maryland Department of Forests and Parks, a "wedge" for the 

future. Land has been zoned for industrial parks and residential 

areas, and some areas are in the process of development as "corridors." Here and there is an area whose population is rapidly increasing and which merits consideration as a "metrotown" by the Baltimore 

Regional Planning Council. Most planners envision northern Baltimore County, above the latitude of Prettyboy Dam, r,s remaining 

more or less rural for the next 50 years, with an average of 5 acres 

per household.

Population Forecasts

Population forecasts are the usual base for predicting future demands on the resources of an area, water very much included. 

Several estimates have been based on the 1950 and 1WO censuses. 

The 1950 estimates consider but do not reflect the trend, although 

already apparent in 1950, of accelerated growth of the suburbs at 

the expense of the city. The 1960 estimates do reflect tl Q, trend, but 

vary as to when it will be reversed to show population increases for 

the city of Baltimore.

Actual 1950 and 1960 census totals for the city of Baltimore and 

three forecasts which vary markedly are shown in figure 32. The 

estimates based on the 1950 census are much higher than the ones 

based on the 1960 census, when the continuing downwr.rd trend in 

the city's population became more apparent. The estimate by the 

Baltimore Bureau of Water Supply of slightly over a million people 

in the city by the year 2010 has been accepted as the most realistic 

figure for Baltimore.

The three forecasts shown in figure 33 for Baltimore County are 

quite uniform, primarily because all three were based on the 1960 

census. If the 1970 and 1980 estimates of the Maryland State Plan54:
1,400,000

1,300,000

900,000

1950 1960 1970 1980 1990 2000 2010

FIGURE 32. Population forecasts for Baltimore City to 2010. A, From the Maryland State Planning Commission (1959). B, From Requardt, Shaw, and Wolman (1953); estimated increase from 1950 to 2000 is 36.9 percent. C, From the 

Baltimore City Bureau of Water Supply (1962); estimated increase from 1960 

to 2010 is 9.9 percent.

ning Department are extended in a straight line to the year 2010, 

the forecast is only 40,000 higher than the lowest estimate, which 

was computed by the Baltimore City Bureau of Water Supply. The 

population of the county by the year 2010 will probably be nearly 

1.1 million.

Two forecasts for the Baltimore metropolitan area (fig. 34) differ 

by little more than 100,000 for the year 2010, even though they were 

computed on census figures for different decades. In general, they 

anticipate that the population of the metropolitan area will be about 

2.3 million in the year 2010. Domestic water needs will average 230 

mgd, and commercial and industrial demands for fresh water will 

be about the same, a total water need of 450 million gallons on an 

average day.

To forecast the population in the Gunpowder Falls basin of the 

year 2010 (fig. 35), the Baltimore County Office of Planning and 

Zoning estimates of election-district populations in 1980 were 

adapted to apply only to the election-district areas lying within the 

basin (the same method used in computing the 1960 total in fig. 3).

55
1,200,000

1,000,000

800,000

600,000

400,000

200,000

1950 1960 1970 1980 1990 2000 2010

FIGURE 33. Population forecasts for Baltimore County to 2010. A, From 

the Maryland State Planning Commission (1959). B, From the Baltimore 

County Office of Planning and Zoning (1962). C, From the Baltimore City 

Bureau of Water Supply (1962); estimated increase from 1960 to 2010 is 

118.3 percent.

2,500,000

2,250,000

2,000,000

1,750,000

1,500,000

1,250,000

1950 1960 1970 1980 1990 2000 2010

FIGURE 34. Population forecasts for Metropolitan Baltimore to the year 

2010. A, From Requardt, Shaw, and Wolman (1953); estimated increase 

from 1950 to 2000 is 72.8 percent. B, From Baltimore City Bureau of 

Water Supply (1962); estimated increase from 1960 to 2010 is 63.2 percent.

56
250,000

200,000

z 

g ij 150,000

Q_

£

100,000

50,000

A W\ 85,000

150,000

240,000

1950 1960 1970 1980 1990 2000 2010

FIGURE 35. Population forecasts for the Gunpowder Falls basin to the 

year 2010. A, Election-district census count (fig. 3). B, Election-district 

count from estimates of the Baltimore County Office of Planning and 

Zoning (1962); estimated increase from 1960 to 2010, is 182.4 percent.

The next step was to extrapolate in a straight line the 1960 computation and the 1980 estimate to 2010. A reasonable prediction is that 

nearly a quarter of a million people will live in the basin 50 years 

hence. This figure may even be too conservative if the planned 

metrotowns prosper. Population predictions for the four areas considered are:

Area

Population

Baltimore f!it.y

Gunpowder Falls basin _

1960

940,000

500,000

1,400,000

85,000

1980

950,000-1,000,000

750,000- 800,000

1,800,000-1,900,000

150,000

2010

1,000,000-1,375,000

1,000,000-1,075,000

2,250,000-2,400,000

240,000

Projects and Plans

Increasing population means increasing demands on water by 

"people at work, at play and at home" (Requardt, Shaw, and Wolman, 1953, p. 7) and increasing difficulties in the maintenance of a 

high-quality water supply. Many of the major demands and difficulties have been anticipated, as is shown in the following discussions 

of projects and plans which have either been activated or approved 

in principle. There are inevitable interrelationships and counterinfluences among the different plans involving water supply, the Gun57
powder Falls State Park, traffic arteries, and zoning. This report 

does not go into the detail needed in an engineering plan; however, 

the engineering plan for a single-purpose project (such as a water 

supply or a State park) usually considers other planning objectives 

only in a collateral way. We have tried to present the overall aspects 

of the diversified subjects as useful preliminaries to future considerations by others.

Water for the Metropolis from the Susquehanna River

Projections indicate that the metropolitan population will increase 

from the present level of 1.4 million persons to 1.8-1.9 million in 1985 

and 2.2-2.4 million by the year 2010 a 50 to 60 percent increase in 

the next 50 years.

Water needs for the metropolitan area will double or triple by 

2010. The predicted demands range from 460 to 525 million gallons 

in an average day. The present demand is 210 mgd. The most conservative prediction by the Bureau of Water Supply assumes a rate 

of increase in demand for the next 50 years of 4.8 mgd per year. 

The increase for the 50-year period 1910-1960 was about 2.8 mgd per 

year. The maximum decade of growth was 1938-48 when the 

demand increased about 6 mgd per year. When the population 

increased only about one quarter of a million, from 1950 to 1962, the 

demand increased about 2.5 mgd per year, about one-half the predicted rate for the next 50 years (fig. 36). The Bureau of Water

500

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

FIGURE 36. Water used by Metropolitan Baltimore from 1900 to 1962 and 

projected to 2010. Photograph by the Maryland Port Authority, Baltimore, 

Md.

58
Supply foresees either an increase in the per capita use of water or 

an increase in demands for water from industry.

To meet this anticipated demand the metropolitan area will be 

using water from three sources: The Patapsco River, the Gunpowder 

Falls, and the Susquehanna River. The Patapsco and Gunpowder 

Falls potentials for water supply have already been considered (p. 

19).

Susquehanna River water will be available to Metropolitan Paltimore by 1966. The Baltimore Bureau of Water Supply has secured 

rights for 250 mgd through a pipeline now under construction, with 

an option to double the amount by the end of the century.

Plans have been made to provide for all the water the city will 

need, both the metropolis and the surrounding and expanding 

service-area neighborhoods, until well past the turn of the century 

(table 4). The Susquehanna water will be made available by withdrawal from the Conowingo Reservoir upstream from the wes4: end 

of the Conowingo Dam, 33 miles northeast of Baltimore and about 

10 miles from the north end of Chesapeake Bay. An aqueduct 144 

inches in diameter will conduct it to a diversion point below the dam. 

From there the first pipeline, 108 inches in diameter, has been extended south and southwest to follow the Fall Line to Baltimore. 

The pumps being installed will be capable of forcing 240 mgd 

through the main. The amount delivered to Metropolitan Baltimore 

will probably be about 220 mgd, 20 mgd being allowed for leakage, 

maintenance interruptions, and the Harford County taps.

TABLE 4. Water supply needed for Metropolitan Baltimore, in million gallons per day

Source of data:

Requardt, Shaw and Wolman 

(1953.-- . -

Oeyer (1959) .

Authors' projection _____ --..

Source of water: 

Gunpowder Falls (Loch Raven 

Dam)... __ .................

Patapsco River (Avalon-pump

Total water available _ _ - -

U950

187

148

50

198

11960

211

148

95

243

250

1970

285

250

220

105

220

549

1980

340

300

220

105

220

549

1985

321

483

1990

400

350

220

105

440

769

2000

460

463

400

220

105

440

769

2010

460

450

220

105

440

769

738

i Actual.

The Susquehanna water will be more expensive than water from 

the Patapsco River and Gunpowder Falls. It is acquired 33 miles 

away and must be pumped from the 45-foot elevation at the source

784-926 O 59
to the Montebello Filtration Plant at a 215-foot elevation. Pumping 

is not the only additional expense. The costs of tho, pipeline, the 

pumps, and their maintenance are important considerations. Another 

expense, difficult to compute at this time, involves the purchase of 

needed water from the Philadelphia Electric Power Co., which constructed the Conowingo Dam, when the maintained flow over the 

dam is less than the minimum needed by the hydroelectric plant. 

The city will attempt to draw water only during high-flow periods 

or when the plant is not operating. Fortunately, the Susquehanna 

is a large river; the lowest weekly flow expected in a 30-year period 

is 1.1 billion gallons per day.

Demands of industry may hasten the construction of a second pipeline to the Susquehanna. Present industries will expand and new 

industries will be located along the Fall Line, all needing water. 

Some consideration is being given to placing the second aqueduct 

farther inland where it can provide raw water to th°, existing and 

planned communities in the northern parts of Baltimore and Harford 

Counties.

Five taps are being made in the pipeline under construction to 

augment or replace local water supplies along the Fall Line in 

Harford County; 10 mgd is the agreed-upon total maximum draw 

from the five taps.

Susquehanna water will be a fine reserve, an additior to the present 

supply for the expanding urban area. The City of Baltimore Bureau 

of Water Supply plans to extend existing mains to serve a larger 

area (fig 17). This extension will permit a more concentrated population west and south of Loch Raven Reservoir and along the south 

side of the lower Gunpowder Falls. The Bureau of Water Supply 

plans to draw as much water as possible from the Gunpowder Falls 

and Patapsco River before using the Susquehanna line. The practical intent of the Bureau is to use all the available cheaper and 

better water before drawing from the Susquehanna, and the Bureau 

makes no allowances for other interests in the basin. Possible compromises are discussed on pages 75-80.

The Gunpowder Falls State Park

Another firm plan is to create a State park in the valley-bottom 

parts of the Gunpowder Falls and Little Gunpowder Falls basins. 

The State government has appropriated funds for tH purchase of 

more than 10,000 acres of desired properties. Figure 37 shows the 

locations of the disconnected sections on the estuary, Little Gunpowder Falls, Loch Raven Dam to the Fall Line of GunpowderFalls, and the stretches on each end of Prettyboy Reservoir. The

60
Reservoir holdings

State park acquisitions

FIGURE 37. Present and proposed recreational areas in the basin and in the 

adjoining Little Gunpowder Falls basin. (Adapted from Alien, 1958.)

existing publicly owned acreages around the reservoirs controlled by 

the Bureau of Water Supply, total an additional 11,400 acres and 

are a fine supplement to the proposed park, but they have a more 

limited recreational use because of restrictions enforced to maintain 

the quality of water in the reservoirs.

Not every rural area is suitable for a State park. City dwellers 

want easy access to a pleasing countryside which is not fenced and 

posted against trespassing. It should have a stream or lake or bay, 

one or more good viewpoints, a fine stand of trees, some wildlife.

61
"The general environment must be such as to promote a feeling of 

completely informal, relaxed, outdoor living" (Alien, 1958, p. 5).

The proposed park possesses a fair share of the desired attractions. 

Plans call for a network of approach roads (but no new valley 

roads) and convenient trails to many picnic and a few camping areas. 

Hiking, riding, and fishing will be encouraged, and several public 

swimming pools may be built. A beach and boating facilities will 

be developed on the estuary.

The park may be divided into two sections: the part above Loch 

Raven Dam where recreational activities must be restricted in order 

to protect the water supply, and the part below the dam where the 

demands of the water supply will lessen seasonally many of the 

recreational facilities for which the State park is being designed.

This State park is now in the process of being created, but present 

thinking varies on how much recreation can take place in it. Watersupply authorities emphasize the need for protection of a vital 

resource; they regret the pending drawdown of the reservoirs and 

the lack of water in the lower Gunpowder Falls, the limitations to 

recreation but they do not want to yield on their requirements and 

restrictions.

Public officials and community leaders who realize that Metropolitan Baltimore now has a deficiency of open space and recreational 

areas want to see the Gunpowder Falls park lands reserved and protected. Some believe it sufficient now merely to acquire the properties, which they think may be developed, or resuscitated, in the 

future when demands are greater and improved technological knowledge may be applied. Others would go so far as to advocate extensive recreational development now, even to swimming in the 

reservoirs.

Zoning and Related Legislation

All Baltimore County has been zoned into areas reserved for industrial, commercial, residential, rural or agricultural, and recreational 

or open-space purposes. This zoning is based on what exists in 

specific locations today and on trends. It is guided by population 

records and forecasts, present traffic lines and plans for extensions 

or changes, existing and planned public services such as water and 

sewer mains, and economic considerations such as land values and 

land use and accessibility to offices and markets.

Planners realistically make allowances for special interests and for 

the ingrained tendency, known as urban sprawl, to expand along 

lines of opportunism, convenience, and least resistance. However, 

more and more legislation is being enacted to reenforce zoning. 

Some measures are palliative and interim, and are recognized as

62
such; practicality discourages close approximation to an ideal, even 

if an ideal condition is comprehensible at this time. Proposed legislation, currently receiving serious study, stipulates a minimum of 1 

acre, 2 acres, or even 5 acres, in some localities, before granting permission to build a house dependent on well water and a septic tank. 

This legislation would lessen the chance of pollution of the groundwater resource and thus protect health. In time, however, it may 

become more a restriction than a safeguard: it could prohibit the 

growth of a population dense enough to finance the ultimately needed 

public water and waste-disposal systems for a community. As 

pointed out by Geyer (1959, p. 37), one family per acre is not economically sound now if pressures exist which will result in rezoning. 

Present plans involving zoning, the future water supply, th?- traffic 

network, and so on, also consider waste disposal interim sewagetreatment plants and an ultimate network of interceptor sewers. 

These plans will obviate reliance on the questionably efficient individual septic tanks for most of Baltimore County south of the 

Loch Raven Dam by 1975 at the earliest, or more probably by 1985; 

estimated annual costs per customer range from $61 in 197? to $45 

in 1985 (Haney, 1962, p. 41). Figure 23 shows the existing sewer 

system as well as planned extensions.

Highways, Byways, and a Bridge

Another complex of reasonably firm plans is illustrated by figure 

2 which indicates in a general way the highways and throughways, 

the byways and bypasses planned by 1985 when an estimated 850,000 

cars will be driven in the metropolitan area.

Highways are the avenues of probable population growth, and the 

site of consequent problems of water supply and demand. Tl Qy pose 

erosion and sedimentation problems; thousands of tons of mud and 

silt may be washed into existing reservoirs and ponds during the 

period of construction, which may last a year or more. THy may 

permit water pollution inadvertently; for example, a truck carrying 

oil or chemicals may be wrecked in a tributary draining to a reservoir. 

They may even deter population growth locally, as well as be conducive to it. The Planning Commission of Kent County, on the 

Eastern Shore, is recommending the construction of a bridge across 

the northern Chesapeake Bay to provide more rapid access to Baltimore. If this bridge is built, possibly by the year 1985, it would 

provide access to a new and attractive Eastern Shore residential area 

less than an hour's commuting time away for workers in Metropolitan Baltimore. Opening this area would lessen pressure on the expansion of suburbia in the counties encircling the city.

63
Suburbs and Metrotowns

Metrotowns are visualized as "cohesive urban developments, larger 

than traditional towns and smaller than modern cities * * * deployed 

radially and in a series of rings around the city of Baltimore * * * 

Metrotowns would contain concentrations of population 100,000 to 

200,000 persons each at higher densities than now found in suburban communities" (Baltimore Regional Planning Council, 1962. 

p. 2-3).

Urban development has been taking place along the western and 

southern sides of Loch Raven Reservoir, in the Gunpowder Falls 

basin, at an accelerating rate during the last 20 years. Existing 

communities, population expansion, proximity to tl Q, extending 

public services of Metropolitan Baltimore, a steadily improving road 

network all are conducive to the local growth of suburbs and small 

cities. By 1985, if present forecasts are accurate, the br.sin will contain one growing metrotown, half or more of two others, and a small 

fraction of a fourth. Planners and public officials knov^ all too well 

that zones can be rezoned and frequently are. They also know that 

if they have been realistic and thorough, their forecasts and plans 

will serve as guides, and will materialize as a generalized whole 

rather than in particulars. Thus, figure 38 depicts the thinking, as 

of February 1963, of the Baltimore Regional Planning Council and 

the Maryland State Planning Department concerning probable urbanization of the Gunpowder Falls basin by 2010. A quarter of a 

million people will be living in the basin by 2010 and at least half 

of them will look to Metropolitan Baltimore for their water supply.

Brief appraisals of proposed metrotowns are necessary preliminaries to forecasting effects on the basin's total water resources. The 

Baltimore Regional Planning Council visualizes various metrotown 

areas as probable sites for planned urbanization. Planners should 

know the amounts of water available and needed locally, the prospects of erosion and of accelerated sedimentation of tie reservoirs, 

the probability of increasing pollution (and supply) from stormwater runoff from impervious surfaces. Some aspect? of four of 

these possible metrotown areas are discussed below; some advantages 

and disadvantages of each are listed in table 5.

Reisterstown

Reisterstown and vicinity is considered by the Baltimore Regional 

Planning Council as the center of a metrotown which will extend in 

all directions from the height of land between the Patap^co, Gwynns 

Falls, and Gunpowder Falls basins (fig. 38). The metrotown will be 

contained more or less within election district 4. Earl^ growth is
10123 MILES

i.l I I J

Adapted from Baltimore Regional 

Planning Council (1962) BALTIMORE

An alternate site selected 

by the authors

FIGURE 38. Possible metrotown sites within the Gunpowder Falls basin.

already extending northwest from Baltimore along U.S. Highway 

140. Growth probably will be more rapid after completion of a 

paralleling expressway and a second circumferential beltway (see 

fig. 2) which will speed up transportation.

Only a tenth to a fifth of the Keisterstown metrotown will be 

within the Gunpowder Falls basin. Topography, and the present 

and planned arterial highways, suggests that this fraction will be 

primarily residential there will be some shopping centers but no 

industries. This fraction will be composed of some 20,000 people on 

approximately 4,000 acres by the year 2010.

65
TABLE 5. Suitability or readiness of metrotown sites for urbanization

Item

Accessibility to downtown Baltimore (mileages from Union Station) .

Topography and elevation (feet above msl).

of importance).

Planned development, other than urban.

shed. 

Probable effects on State

park. Recreational potential

Reisterstown

17 miles (to junction of U.S. 140 and Md. 30). Present roads to be sup- plemented by Expressways and the 2d circum- ferential highway.

Gently rolling highland, 490 to 635.

farms.

tries. Water main. Sewage treatment plant. Industrial park; metro- politan sewerage service.

gravity main to city's network planned by 1970.

runoff pollution of Loch Raven Reservoir.

Easy access to Liberty Reservoir and the State 

park.

Carney-Perry Hall

11.5 miles (to Perry Hall). The John Kennedy Me- morial Highway, recently completed, now supple- ments U.S.I and U.S. 40. 

Harford Road serves the 

Carney section. Rolling upland ridge, 250 to 485.trial.water mains. Sewer line 

under construction. 

Metropolitan water and 

sewerage networks.

mains; extensions are planned.

tion connection with city's network under construction for part of area; local treatment plants for other parts planned by 1970. Gunpowder Falls gravity main by 2010.

pollution. Easy access to Loch Raven Reservoir and to lower sections of the State park, including the estuary.

Towson-Cockeysville

11 miles (to Texas). Served by the York Road and the Baltimore-Harrisburg Expressway. The 2d cir- cumferential highway will skirt Cockeysville.Valley bottom and uplands, 270 to 500.

trial Park. Water main. 

Sewer line. 

Expanded industrial park...

tension of city main to Ashland is planned.

Timonium. Force main to city's network serves most of the community.

of Loch Raven Reservoir. 

Storm-runoff pollution.

Easy access to Loch Raven and Prettyboy Reservoirs and to the State park.

Hereford-Belfast

20 miles (to Hereford). Served by the York Road and the .Baltimore-Harrisburg Expressway. The 2d circumferential will 

skirt the south boundary.

Rolling uplands; varied, 320 to 690.

Circumferential highway along south boundary. East-west Expressway through center.

from Ashland is planned.

force main from Cockeys- ville after 1970.

Accelerated sedimentation

of Loch Raven Reservoir. 

Storm-runoff pollution.

Easy access to both reser- voirs and to upper section of the State park.

Long Green Valley

15.5 miles (to Hydes). Present 2-lane roads will 

connect with the 2d circumferential highway 

near Glenarm.

2 valleys and uplands, 275 to 575.

trial.

Circumferential highway through the southwest part.

mains from Cub Hill or 

Perry Hall are possible.

Falls gravity main by 2010.

None.

Sedimentation and runoff

pollution. Easy access to Loch Raven Reservoir and to lower sections of the State park, including the estuary.

OS

OS
Carney-Perry Hall

The Carney-Perry Hall area, northeast of Baltimore City, is a 

scene of present suburban development. The scattered residential 

areas and small communities eventually may be consolidated into a 

metrotown (according to the Baltimore Regional Planning Council), 

much of which will be south and outside of the Gunpowder Falls 

basin. Approximately 40,000 people will be living in residential 

subdivisions on about 8,000 acres within the basin by 2010. Accommodating shopping centers will be constructed; few if any industries 

are anticipated.

Towson-Cockeysville

A metrotown already is being centered on Towson. Northern 

Towson and small but growing communities extending north along 

the ridge between Loch Raven Reservoir and Beaver Dam Run, 

along the York Road and the Harrisburg Expressway, are within 

the Gunpowder Falls basin (fig. 2). The area is growing rapidly; 

it already includes more than 20 named residential sections either 

established or being developed, a large quarry, and a cluster of light 

industries that form the core of what will be an extensive industrial 

park. At least 100,000 people will probably be living on the approximately 20,000-acre part of the metrotown within the basin by the 

year 2010. Some of these people today have homes less than 200 

yards from the shore of Loch Raven Reservoir. The growth of this 

metrotown merits careful attention if the Gunpowder Falls water for 

the metropolitan supply is not to suffer in quality.

Hereford-Belfast Road

Another metrotown has been planned for the Hereford-Pelfast 

Road area, which is between Prettyboy and Loch Raven Reservoirs 

and west of the Gunpowder Falls stream and is bisected by the 

Harrisburg Expressway. The second circumferential highway 

around Baltimore, and Western Run valley, will separate thir small 

city from the larger Towson-Cockeysville metrotown to the south. 

About 60,000 people will live in the community by the year 2010, on 

approximately 12,000 acres of the Gunpowder Falls basin.

PROBLEMS, CHOICES, AND COMPROMISES

The Gunpowder Falls basin, as visualized in the year 2010, will 

provide (1) much of the water supply for almost 2.5 million people in 

Metropolitan Baltimore, (2) nearly 100,000 homesites, aid (3) 

approximately 25,000 acres of out-of-doors for recreational purposes. 

Plans (table 4) call for the distribution of roughly four-fifths cr more 

of the basin's streamflow in the Metropolitan Baltimore ar°,a. A

67
quarter of a million people will be living in the basin, 80 to 90 percent 

of them in metrotowns. The largest open spaces, aside from the rural 

northern third of the basin, will be the reservoir reservations, totaling 

15,300 acres, and the 10,000-acre State park. Water supply, living 

space, and recreational facilities are interrelated; people require all 

three, and competition among them results as demand'? or pressures 

increase.

Living Space Versus Water Supply

Urban development and maintenance will undoubtedly affect the 

quality of the Gunpowder Falls water resources, and to a lesser 

extent, the quantity of the water. The pollutants (other than 

sewage) that storm-water runoff carry into the streams and the tests 

that were made to determine the kinds and locations of pollutants 

already present in Loch Eaven and Prettyboy Reservoirs have been 

discussed (p. 37). As local communities grow, the amount of pollutants that enter the streams and reservoirs will increase. Erosion 

and sedimentation in the area have been discussed also (p. 46); 

although the situation today has improved, further urbanization of 

the basin may introduce a potential sediment problem that could be 

detrimental to the water supply. As an alternative, the possibility 

of constructing a metrotown in the Long Green Valley subbasin, which 

drains into Gunpowder Falls below the Loch Raven Reservoir, 

deserves consideration because urbanization there wculd not contribute pollutants and sediments to that part of the Gur powder Falls 

basin used for Metropolitan Baltimore's water supply.

The Potential Sediment Problem

The Gunpowder Falls basin has a high sediment-yield potential 

when the land is subjected to certain uses. Yields at present are 

modest. The water-supply reservoirs have large capacities, and they 

will remain efficient far into the future (see fig. 31). Net so the small 

watershed impoundments, which provide water for irrigation, storage for flood control, sediment detention, stock, fishirg, and other 

recreational pursuits. Brune (1953) has shown that tb<> percentage 

of sediment trapped in a reservoir is closely related to the impoundment's capacity and the annual inflow, that is, on any given stream, 

small reservoirs will fill with sediment faster than lar^e ones, even 

though the former retain smaller percentages of the sediment flowing 

into them. The amount of loss in reservoir capacity that may be 

expected when various percentages of the basin change in character 

from rural to urban, assuming a yield of 25,000 tons of sediment 

from each square mile that undergoes urbanization, is indicated in 

figure 39; sediment retentions for normal ponded reservoirs of

68
100

5 10 

SEDIMENTATION INDEX

100

Capacity of reservoir (million gallons) 

Drainage area (square miles) =Sedimentation index

_, , 100 million gallons , . ,. ^ ., . , . Example: ^ =10 (sedimentation index.)

FIGURE 39. Chart of capacity loss to sediment in small impoundments because

of urbanization.

Example: Percentage of drainage area to be urbanized equals 50. Find sedimentation index of 10 on figure; follow line up to 50-percent urbanization 

curve; follow left on a horizontal line to the left margin. Approximate loss 

of reservoir capacity is about 20 percent.

different sizes were taken from Brune (1953, p. 414). For example, 

reservoirs with capacities of less than 5 million gallons per square 

mile of drainage area (sediment index equals 5) may lose 30 percent 

of their capacities when 50-percent urbanization takes place 

upstream.

Large amounts of sediment affect the aquatic-life balance of a 

reservoir, particularly if the sediment includes a high percentage of 

fine clay which may stay suspended for several weeks and give the 

water a cloudy appearance. Turbidity prevents sunlight from penetrating the water, oxygen levels are reduced, feeding and spawning 

habits of varieties of fish are disturbed, and undersirable species 

become dominant. Thus the ecology of a reservoir may change for 

the worse, and many years may be required for the reservoir to

69
400

81

300

200

200 300 

PERCENTAGE INCREASE IN URBANIZATION

400

FIGURE 40. Projected annual sediment yield for the basin below Prettyboy 

Dam for 1960-2010 as urbanization increases.

return to the former healthy condition if it has not lost most of its 

capacity during the period of urban development.

The anticipated threefold increase in population by the year 2010, 

and resultant urbanization, will increase the basin's sediment yield 

about 30 percent. If population growth were not a factor, the 

present yield of about 235 tons of sediment per square mile per year 

from the area below Prettyboy Dam would remain constant, or more 

probably diminish. As new construction keeps pace with the population growth, the sediment yield will average between 275 and 325 

tons per square mile per year. Sediment yield for the doubling and 

quadrupling of the population is estimated in figure 40. This figure 

is drawn on the basic assumption that during the period of urbanization a decrease of about one-third in sediment yield from rural sections will be more than compensated by an increase from the urbanized areas to give a new sediment rate about a third greater than the 

present rate. Sedimentation will not be a basinwide problem, but it 

will create local problems, particularly where small reservoirs and 

ponds are adjacent to the several planned metrotowns.

An Alternate Metrotown Site .

Sedimentation and storm-water runoff may or may not become 

important factors in the water supply in the coming 50 years, but 

urbanization does change the hydrologic environment. The adverse

70
consequences are sufficiently serious to warrant discussion of the 

hydrologic effects of alternative possibilities, even some which may 

not presently be under definite consideration. The effects of additional large communities metrotowns in the Gunpowder Falls 

basin upstream from Loch Raven dam should be compared with 

those of alternative areas.

A hydrologic evaluation of Long Green Valley, east of Loch Raven 

Reservoir and draining below the dam, indicates that it is one alternate site for a metrotown which holds to a minimum the conflict 

between urbanization and water supply. An appraisal of this site 

for urban development focuses attention on the hydrologic factors 

that city planners should consider assuming that urban growth can 

be guided.

Long Green Valley, in its upper reaches, is an oval basin resulting 

from the weathering of a pocket of Cockeysville Marble; it is rimmed 

by hills and ridges composed of the more resistant Wissahickon 

Schist. Hydes Post Office is a convenient central point of reference 

(see fig. 2). A similar but narrower valley to the south, centered on 

the community of Glenarm, parallels the Hydes basin and also overlies deposits of marble. Long Green Creek drains both valleys as it 

flows southeast, through an increasingly steep ravine, to join the 

main Gunpowder Falls about 5 miles below the Loch Raven Dam. 

The combined Hydes and Glenarm areas, and the slopes rimming and 

separating them, total about 20 square miles 13,000 acres which 

could accommodate as many as 60,000 people (fig. 41).

Farms now occupy most of the bottom lands. A metal-container 

machinery factory and a metal-parts finishing company are located 

at Glenarm. Extensive estates and several residential developments 

(along the western and northern rims of the Hydes basin) dot the 

deforested highlands. The bed of an abandoned railroad traverses 

the two basins in a north-south direction; it crosses the Gunpowder 

Falls approximately 1.5 miles below Loch Raven Dam.

Neither sedimentation during construction nor storm-water runoff 

would affect the metropolitan water supply because the entire area 

drains below Loch Raven Reservoir. They could pose problems in 

the lower reach of the planned Gunpowder Falls State Park.

The Long Green population would be dependent upon water from 

wells during the initial growth period, until 1985 or 1990, when the 

expectancy of 25,000 residents would have a water requirement of 

2.5 mgd.

The low base flow of a stream represents the safe long-term 

ground-water yield of an area if this water can be pumped from 

wells instead of being allowed to flow away overland. The low flow

71
FIGURE 41. Long Green Valley, a possible alternate metrotown site.

72
of streams draining areas underlain by the weathered Cockeysville 

Marble is greater than streams of comparable size that drain areas of 

different geology (p. 14).

The low-flow part of a duration curve applicable to Long Green 

Creek (fig. 42) shows that the flow exceeds 2.0 mgd and may be as 

high as 2.5 mgd for 95 percent of the days during the year. Estimated on the basis of a 95-percent flow, the ground-water yield from 

properly sized, spaced, and developed wells in the area would be as 

much as 2.5 mgd. The wells should be located along the stream, in 

the downstream end of Long Green Valley, to capture the maximum 

amount of water. An estimated 10 to 15 wells should deliver the 

needed amount of water (see p. 74).

In determining the flow that is exceeded 95 percent of the time, 

the 5 percent of the time when the flow is less than the 2,0 to 2.5 mgd 

must also be considered. Low flows usually occur during dry periods 

in late summer.

10.0

9.0 

8.0 

7.0 

6.0 

5.0

4.0

3.0

2.0

1.0

50 60 70 80 90

PERCENTAGE OF DAYS

95 98 99

FIGURE 42. Low streamflow from Long Green Valley at Gittings, 

showing percentage of days when flow exceeds the amounts in 

the left column.

73
A 6-inch-diameter test well at Hydes, drilled to a depth of 165 feet, 

produced 85,000 gpd (60 gpm) with 43 feet of drawdown. A 12-inch 

well properly constructed and developed at the Hydes site should 

produce more than twice1 this quantity. The soil mantle at this location is 127 feet thick; from 127 to 165 feet the well is drilled in solid 

marble. The records on the Hydes well, coupled with sparse data on 

other local wells, indicate that the valley sediments may average 

about 100 feet in thickness over an area of approximately 6 square 

miles. The top 50 feet of this aquifer contains from 3 to 6 billion 

gallons of water. This amount of water in storage is more than 

adequate to sustain 2.5 mgd yields through occasional dry periods.

These estimates are preliminary. In order to determine the yield 

more precisely, additional study should include:

1. A better definition of the low flow of Long Green Creek. A 

gaging station operated near the Gittings bridge for a minimum of 1 year would provide this information.

2. Test drilling to find out the thickness and extent of the mantle 

of decomposed marble in the valleys, to permit a closer 

estimate of the ground water in storage, and well-yield 

expectancies.

3. Determination of the permeability of the sediments in different parts of the valley, to compare with the records of the 

Hydes well.

4. Determination of the induced recharge potential along Long 

Green Creek, particularly at the lower end of the valley 

near the Gittings bridge.

At present the Hydes Post Office is 5 miles from the nearest water 

mains of the Baltimore system (Perry Hall or Cub Hill). If water 

is provided through extension of the metropolitan network by the 

end of the century, the old railroad line might provide a once-defined 

right-of-way for a water main to the Glenarm and Hydes area; or a 

tap from the second Susquehanna pipeline, if the line is routed 

inland, might serve the area.

Waste disposal from Long Green Valley should not be dependent 

upon septic tanks if population growth is encouraged and if well 

fields are used. A local waste-treatment plant might suffice for the 

next 20 to 25 years, but there would be objections to the disposal of 

the effluent in the waters of the State park. An interceptor connection with the Perry Hall pumping station (fig. 23) which would be 

connected to the Back River sewage-treatment plant of the metropolitan system is a possible solution. At some later date, if the 

proposed Gunpowder Falls interceptor to a treatment plant on the 

Gunpoyder River estuary becomes a reality (p. 33), the Long Green

74
metrotown would be served by a system functioning entirely by 

gravity flow.

Water Supply Versus Recreation

The increasing pressure for more recreational space and facilities 

raises problems that concern the best interest of the water supply 

which requires keeping water as pure and as cheap as possible. Increased recreational use of the water supply would result in increased 

pollution which would necessitate additional treatment of the water 

at more cost. Recreational and aesthetic pressures might also result 

in lessening the amount of water available for the mains of metropolitan Baltimore if low drawdown of the reservoir water levels was 

strongly criticized. When Susquehanna water is available, compromises will be possible if the public is willing to pay for tl Qm.

Draft Rates and Water Levels

The draft from Liberty Reservoir on the Patapsco River is approaching its upper limit (p. 23, fig. 18). The present draft rate 

of 105 mgd will result in a deficiency about once in 10 year?, a draft 

of 110 mgd would cause a shortage about once in 5 years, and a 117- 

mgd draft about once in 3 years. Frequent deficiencies wonld mean 

increased costs and problems in distribution-system operation and 

maintenance. The draft on the Patapsco probably will be stabilized 

at about 105 mgd, which has a 1 year in 10 chance of deficiency.

In other words, the Gunpowder Falls will supply additional water 

to meet the demands of the growing metropolis; it is capable of a 

much higher draft rate (p. 25, fig. 19). Figure 36 show? the predicted water demand for Metropolitan Baltimore from 1960 to 2010. 

The middle years of the forecast zone were used for the following 

calculations:

1. Loch Raven Reservoir is capable of supplying th°s present 

(1964) demand without reliance on water released from 

Prettyboy Reservoir. In fact, there is only a l-in-20 chance 

that Loch Raven will not be able to supply this demand 

when using only the top two-tenths of the reservoir's 

capacity, which is equal to the top 6 feet of the pool.

2. The demand from the Gunpowder Falls water-supply system 

will be about 150 to 170 mgd in 1970-75, and release of 

water from Prettyboy Reservoir will become increasingly 

essential to the Gunpowder Falls water-supply system. 

During this transitional period of increasing demand, the 

water-supply engineer will have to decide how much the

784-926 O 66 6 75
Loch Raven water level should fluctuate; maintenance of a 

fairly stable water level will mean an increased use of water 

from Prettyboy Reservoir.

3. By 1980 the demand on Gunpowder Falls will b**, about 200 

mgd. This rate will require maintenance of the water level 

in Loch Raven Reservoir within the top few feel of the pool 

in order to have sufficient pressure in the Monteb°Jlo Tunnel 

to supply the required 200 mgcl to the filtration plant. If 

the drawdown of Loch Raven Reservoir is limited to 3 feet, 

releases from Prettyboy Reservoir will be needed 60 to 70 

percent of the year. About 1 year in 6, all the water in 

Prettyboy Reservoir and also the top 3 feet in Loch Raven 

Reservoir would be needed to meet the demand on the Gunpowder system. The total capacity of Prettyboy Reservoir 

plus the top 3 feet of the water in Loch Raven Reservoir 

equals 22 billion gallons (see fig. 15).

4. The chance of a failure of using all the water in both Gunpowder Falls and Prettyboy Reservoirs during s, drought 

would occur about once in 25 years (fig. 43). There is a 

l-in-20 chance that all the water in Prettyboy Reservoir 

and eight-tenths of the volume in Loch Raver Reservoir 

would be required, and a l-in-10 chance that more than 

three-tenths of the volume in Loch Raven Reservoir would 

be required.

5. By 1990-95 the demand on Gunpowder Falls could be 240 to 

270 mgd. The probability that the reservoirs will not be 

able to deliver this amount increases significantly. The 

expectancy of failure of both reservoirs with a d~aft of 240 

mgd is about once in 5 years, and the 270 mgd rate would 

result in failure once in 2 to 3 years. There is some question 

whether the Montebello Tunnel could deliver water at the 

higher rate. Probably 240 to 250 mgd could be realized, but 

with a deficiency once in about 5 years. During periods of 

deficiency, Susquehanna River water would have to be used 

to augment the supply needed by Metropolitan Baltimore.

The water levels in both Gunpowder Falls reservoirs probably will 

fluctuate widely after about 1985. Complete drainage of Prettyboy 

Reservoir can be expected once in 3 to 4 years. Loch Raven Reservoir 

can be expected to be 10 feet below dam crest about once in 5 years, 

and 20 feet below dam crest about once in 6 years. A water level 10 

feet below dam crest would expose about 550 acres of shoreline, which 

is equal to about 20 percent of the reservoir surface. A water level 20

76
(spMl)

240:0

Q

«r 

237,1 E .10'

H 

233,8- j£! '20

" Z " :

o

-23^.5- <» -30

§ -_-

2J 2 g ?0

203 u^ >BO"

*76 t

100

-

r

' 

^

53- 19 I ' <'

'

'

1 - I "!'' * n "J

70' 19

'

*

75' 19

»-->,-.

8G i9

1 - .. :

85 19 ,:'

,

90 19 I ' '

i,

!

,. .,:

95 2000 1 ' " i:: - "j

f

. :-

1

106 125 15© 175 2tKJ ??,!> 25C 

,W M'Ll'ONS OF GALLONS PER DAv

275 '

FIGUEE 43. Relations between draft on the Gunpowder Falls water supply and 

probability that Loch Raven Reservoir contents will fall below indicated 

amounts. Loch Raven Reservoir drawdown values include full use of Prettyboy Reservoir contents. The projected draft rates (bottom scale) are for 

the Gunpowder Falls water-supply system only. ,

feet below dam crest would expose about 950 acres constituting about 

38 percent of the full-reservoir area:

Loch Raven Reservoir water-surface 

elevation (feet)

235-- 

232. 5_ 

230 _ 

227. 5 

225 

222. 5 

220

Acres covered 

with water

2,400

2,200 

2,000 

1,850 

1,750 

1,700 

1,550 

1,450

Land surface 

exposed 

(percent)

£ 

17 

25 

27 

3S 

3£ 

31

Rights to all surface water in the basin and to the construction of 

reservoirs on the Gunpowder Falls were secured many years ago. 

The sole purpose was to provide water for the metropolitan area.

77
Since World War II, however, recreational pursuits have become an 

increasingly important part of the American way of life; land and 

water resources provide the setting. The conservative guardians of 

the Gunpowder Falls water supply have yielded somewhat in recent 

years to allow increased fishing privileges, boat marinas, and picnic 

areas (see p. 52 ). The public, in search of recreation, on the other 

hand, has sought many privileges which were not granted. Recreational demands will become more intense in the coming 20 to 30 

years, when the population doubles. Compromises will be increasingly in order.

Optimum reservoir conditions for recreation would be those in 

which the water level would not be drawn down to expose great 

expanses of bare shoreline. Mudflats are not pleasing sights, and 

they hinder access to the water. In addition, greatly fluctuating 

water levels are particularly undesirable during the spawning periods 

of fish which lay eggs in shallow water. Frequent or prolonged 

changes in reservoir content also can cause changes in the biological 

and physical environments which have undesirable effects on aquatic 

life and water quality.

The conflict between recreational use of Loch Raven and Prettyboy 

Reservoirs and water demand for the metropolitan area will begin to 

be critical about 1980, when the draft rate is expected to be about 

200 mgd. Before then the chance of lowering the Loch Raven lake 

level below the dam's crest will occur in about 10 percent of the years.

Hydrologic analysis suggests that, for recreational purposes, the 

Loch Raven Reservoir water surface should be held above the 233.8- 

foot mark (see fig. 43) which is about 6 feet below the top of the 

dam. For adequate water supply at this level, recreation would have 

to be restricted 1 year in 10. To achieve this level, the draft rate 

must be held to 195 mgd. If the water level were held at the same 

elevation and recreation restricted 1 year in 5, the draft rate could 

be raised to about 212 mgd. (See fig. 43.)

The table below notes that water-surface elevations of 3, 6, and 10 

feet below the dam crest would provide draft rates from 190 to 240 

mgd, depending upon the chance the decision-maker is willing to 

accept in allowing the water level to drop below a selected level.

Level (feet below top of dam)

Chance (percent: years) water will fall below 

indicated level

10; 1 in 10....

20; 1 in 5. _ .

30; 1 in 3 ...

3 6 10

Maximum draft rate permissible 

to maintain level (mgd)

190 

205 

225

195 

212 

235

200 

217 

240
Augmenting the Flow Below Loch Raven Dam

The amount of water flowing in the Gunpowder Falls below Loch 

Raven Reservoir has been greatly reduced by diversion to the metropolitan system. About half the time, mostly during the summer and 

fall, the streamflow is below 10 cfs (cubic feet per second) and the 

water movement is sluggish. During warm summer periods, large 

amounts of algae and slime tend to accumulate in the channel. This 

growth is caused by two major factors: (1) a buildup of the dissolved chemical substances in the water, which are nutrients to plant 

growth, and (2) the amount of water flowing in the stream is insufficient to create enough turbulence to keep the channel flushed. From 

an aesthetic standpoint, this condition is undesirable in a public park. 

On the basis of the runoff record for 1950-60 and the present rate of 

withdrawal from Loch Raven Reservoir for water supply, maintaining minimum flows year round at 20, 15, and 10 cfs could be done by 

releasing about 4.7, 3.0, and 1.4 mgd, respectively. However, it 

would be necessary to augment low flows only during the periods of 

deficiency that occur during the warm months when oxygen levels 

are low, not during other periods. Consequently, only about half the 

above amounts would be needed, that is, 2.4 mgd for a flow of 20 cfs, 

1.5 mgd for 15 cfs, and 0.7 mgd for 10 cfs. Though the amount of 

water involved is small, releases w^ould have to be made during 

critical periods of the year. In future years, water probably will 

seldom be permitted to spill over the dam. Dillution of downstream 

water by releases from Loch Raven would lower dissolved-chemical 

concentrations and provide a more acceptable quality of water 

through the lower parts of the State park.

Additional Impoundments

The recreational facilities available and planned in the Gunpowder 

Falls basin have been listed (p. 52), as well as the recreational pursuits allowed and the restrictions enforced by the Bureau of Water 

Supply. The water-supply demand on Gunpowder Falls may eventually be as much as 240 mgd. The average annual flow at Loch 

Raven is about 260 mgd. The water basin, as presently developed, 

will continue to lose some water to the Chesapeake Bay when high 

water spills over Loch Raven Dam.

Thirty years ago, attention (Gregory, Requardt and Wolman, 

1934, p. 103) was directed to the construction of a water-supply reservoir on Western Run at Butler (see upper right of center, fig. 2); the 

consideration ended primarily because of economic reasons. This 

reservoir would have been equal to Prettyboy in capacity (20 billion 

gallons) and would have yielded about 18 mgd. Perhaps a new look

79
at the Gunpowder Falls is in order, to equate resource potential with 

resource demand through additional impoundments. If economic 

and low-yield considerations ruled out large reservoirs for water 

supply 30 years ago, then certainly the same would hold true today. 

However, inasmuch as recreation, low-flow supplementation, flood 

control, and soil conservation have been receiving more attention in 

recent years, the appraisals of the water resource should be expanded 

accordingly. Topographic and streamflow conditions are suitable for 

the construction of small impoundments, particularly on the Western 

Run and Little Falls tributaries and on the main stream above 

Prettyboy Reservoir. They would:

1. Expand recreational facilities for picknicking, fishing, boating, and other out-of-door sports and amusements. Camping might be permitted around some reservoirs. Sailboats 

and canoes might be allowed on one or more of the lakes. 

Even swimming might be permitted in an upstream impoundment, where the water would have plenty of opportunity to aerate, filter, settle, and purify in streambeds and 

lower reservoirs in its course downstream.

300

250

200 -

150

100

20 40 60 80 100 120 

RESERVOIR CAPACITY, IN BILLIONS OF GALLONS

180

FIGTJBE 44. Amounts that draft rate from reservoirs on Gunpowder Falls can be 

increased with additional reservoir capacities. The curves show the chance, in 

percent, of occurrence of deficiencies; the curves were computed by combining 

the probability of carryover-storage requirements which are based on probability routing of the annual discharge (see Hardison and Furness, 1963) with the 

probability of seasonal requirements.

80
2. Increase the storage capacity of the water-supply system. 

This increase would assist the Bureau of Water Supply in 

maintaining a high draft rate during extreme droughtperiod emergencies (fig. 44).

3. Assist in maintaining an acceptable minimum flow below 

Loch Raven Dam by releasing water into and through Loch 

Raven Reservoir when necessary.

4. Supplement Prettyboy Reservoir in keeping the water level 

in Loch Raven Reservoir at or above the 233-foot elevation 

mark needed to permit gravity flow to the Metropolitan 

Baltimore water-supply system.

Increasing the Patapsco Water Supply

Liberty Reservoir has a high enough water level (the dam crest is 

420 feet above msl) to permit gravity flow to the Ashburton Filtration Plant (353 msl) and to the higher parts of Metropolitan Baltimore. At present the system can supply 105 mgd with a chance of 

deficiency 1 year in 10. When available supply does not meet the 

needs in the higher metropolitan areas, Gunpowder Falls water must 

be pumped into the high-altitude mains at additional expense.

Prettyboy Reservoir captures 70 mgd on an average day throughout the year (fig. 15). A pipeline about 10 miles in length could 

deliver any desired fraction of that amount to the Patapsco drainage 

and thus augment the Liberty Reservoir supply (fig. 45). Releases 

from Prettyboy Reservoir would have to be calculated on the respective needs of the Loch Raven and Liberty water-supply systems; 

however, the draft rate on Liberty could be raised 30 to 40 mgd if 

desired. The water would have to be pumped over the divide, at 

least for the initial lift, until syphoning became effective; thh pumping would have to be done each time water was released from Prettyboy to Liberty because elevations of gaps in the divide approach 640 

feet. Cost probably would prohibit extensive tunneling and an 

extension of 2 to 3 miles of pipeline to achieve inexpensive gravity 

flow (the crest of Prettyboy Dam is 520 feet above msl). Half of 

the Prettyboy Reservoir average daily yield (35 mgd) would permit 

that amount of increase of the draft rate on Liberty Reservoir. Half 

the storage capacity of Prettyboy would increase the present storage 

volume of Liberty (43,000 million gallons) almost 23 percent to a 

total of 52,800 million gallons.

This project would lessen the attractiveness of Prettyboy Lake for 

recreation because the water level in Prettyboy at times would be 

unattractively low. A compromise would be the mainterance of

81
HARFORD CO

1012 3 MILES iii i i i Elevation, 520 ft 

Minimum suitable above msl \ 

divide elevation, \ 

640 ft above msl

Elevation at possible 

pipeline outlet, 500ft / 

above msl

Loch Raven ^Reservoir

Liberty Reservoir

LIBERTY DAM

Elevation, 420 ft above msl

FIGURE 45. Map showing possible route of pipeline that could be built to divert 

water from Gunpowder Falls basin to Patapsco River basin.

attractive high water levels, insofar as possible, in Loch Eaven and 

Liberty.

Recreation Versus Living Space

As yet, there is little competition between urban growth and the 

need for open spaces. Good roads, speedy cars, and increasing 

amounts of free time permit the city dwellers to drive to the countryside or to recreational areas in a fraction of an hour from downtown 

Baltimore. Only the ubiquitous "No Trespassing" and "Posted" 

signs are reminders that the city dwellers' activities in the country

82
are limited, for the most part, to the roads and the few public lands. 

The growth of suburbia, however, is pushing the countryside farther 

and farther away. New housing developments are springing up and 

greatly changing the attractive roadside landscapes. The increasingly common practice of local farmers to sell "front-acre loV the 

strips of land bordering a road or highway as residence sites satisfies the city-worker purchasers who want homes in the country, but 

this practice greatly alters the aesthetically pleasing op'Hn-space 

appearance of a rural landscape.

The State Planning Commission and the Department of Forests 

and Parks have recognized the advisability of reserving lane1 now to 

meet expanding future needs for parks and open spaces. One result 

is the planned Gunpowder Falls State Park, which will supplement 

and increase facilities now provided by the reservoir areas These 

agencies know (see p. 51) that by 1980 there will be a deficiency of 

some 30,000 acres of recreational land 94 square miles and twice 

that by 2010, unless more land is acquired soon, before housing 

developments preempt all the choice sites and before land values 

increase to figures too exorbitant for large-scale purchase. This 

situation applies to all the five counties adjoining the metropolitan 

area.

The Baltimore County Office of Planning and Zoning, ako aware 

of the need for acquiring open space now to meet future needs, has a 

study underway of the actual and potential recreational areas within 

the county. Perhaps this study will result in the setting aside of a 

few thousand additional acres as extensions of the present reservoir 

and planned State park tracts.

It is expected that in 2010 the northern third of the basin will still 

be rural one household per 5 acres, although most farmers probably 

will have disposed of many of their front-acre lots for home sites. 

The State park will be an attractive and popular entity, but further 

recreational space will be needed. The questions are Where and How.

Publicly Owned Additional Impoundments

The construction of more dams in the basin would convert land to 

water-surface area a loss of living space. As the years go by and 

land values increase, the social and economic cost may preclude inundating 1,000 to 3,000 more acres in the drainage area, in addition to 

the 3,900 acres already covered by the water in Loch Raven and 

Prettyboy Reservoirs (fig. 15). Planners of the Gunpowder Falls 

State Park may therefore consider the construction of additional 

impoundments soon, accessible to the public, on suitable rural sites on 

both Gunpowder Falls and Little Gunpowder Falls. Most reservoirs

83
in the larger basin would provide the benefits already mentioned (p. 

80-81). A dam on Little Gunpowder Falls would provide a lake 

where swimming and other water sports would have no tangible effect 

on the Metropolitan Baltimore water-supply system.

An alternative course of action would be to encourage and aid 

builders in the construction of additional impoundments, in conjunction with the expansion of the suburbs and the growth of rretrotowns.

Possibilities on the Estuary

The State park as planned will include the head of Gunpowder 

River the head of the estuary from the east bank of the mouth of 

Gunpowder Falls west to a point about half way up the Pird River 

arm. This east-west airline distance is just under 3 miles; the shoreline mileage is several times greater. Present plans calls for a 

marina and a swimming beach on this park land.

Keeping the water clean should not be too difficult. No pollution 

of consequence is expected from the military installation, which includes the entire eastern shore of the estuary and two of the western 

shore promontories. The two Gunpowder Falls streams will flow 

through a State park, and it can be expected that their water will be 

kept at acceptable State park standards; sanitary conditions in the 

State park holdings on the estuary itself will be controlled. Possible 

sources of pollutants which may merit watching are (1) the primarysewage-treatment plant at growing Joppatowne, (2) the effluentdischarge point from the large sewage-treatment plant, which is 

recommended for construction by the end of the century, to handle 

the waste from the two proposed Gunpowder Falls interceptors (fig. 

23), and (3) the growth of industrial and residential developments 

along the western side of the Gunpowder River estuary, especially 

including the northwestern arm of Bird River.

CONCLUSIONS

The Gunpowder Falls drainage basin, north of Baltimore, is about 

50 miles long, has a maximum width of 16 miles and contains almost 

350 square miles. The headwaters are just inside Pennsylvania, and 

the watercourse drains about half of Baltimore County as it meanders southeast to the Chesapeake Bay. The basin provides water 

and space for living, working, and playing. As the population 

increases in the coming decades, the demand for these water and land 

resources will increase as the needs intensify.

More than 85,000 people now (1964) live in the ba?m threefourths of them occupy an arc of villages and expanding suburbs to 

the south and west of Loch Raven Reservoir, which forms the north-
eastern fringe of Metropolitan Baltimore. The basin is now predominantly rural: 60 percent farmland, 30 percent forest covered, 

and 10 percent urbanized. The comparatively few local industries 

are mostly between Towson and Cockeysville.

The basin receives an average of about 46 inches of precipitation 

per year; about 28 inches are lost through evapotranspiraticn; the 

remaining 18 inches are available as surface and ground water for 

man's use. Thus, the water available amounts to 300 mgd, and to 

264 mgd for the watershed above Loch Raven Dam. The yield 

varies seasonally, being greater in winter when evapotranspiration 

is less. It also varies regionally, although to a much lesser extent, 

with the geology; the areas where marble is prevalent retain and 

release ground water at a more constant rate to maintain flow in 

associated streams than do the areas where igneous and metamorphosed 

rocks predominate.

The upper 80 percent of the basin has been developed almost fully 

as a water supply for Metropolitan Baltimore. No more water will 

be obtained from this area, and the present and future concerns of 

management are protection and regulation. The safe yield has been 

computed at 148 mgd an admittedly conservative figure. The 

present system could supply 200 mgd with a probable deficiency in 

only 1 year out of 20. This higher draft rate would cause greater 

fluctuations in the water levels of the two reservoirs, particularly in 

upstream Prettyboy Reservoir, which is used to regulate Loch Raven, 

but it would lessen the amount of water presently lost by spill over 

Loch Raven Dam. The lower valley, between Loch Raven and the 

estuary, is outside the present water-supply development.

Ground water is available in moderate amounts from wells 

throughout the basin; about 3 mgd are pumped to supply small communities and scattered households. In the part of the basin in the 

Piedmont, wells drilled into the weathered marble provide the largest 

and most consistent yields, averaging about 20 gpm per small well. 

In the narrow part of the basin in the Coastal Plain, the sandy 

aquifer apparently can provide about 250 gpm per large well, but 

sustained heavy pumping might result in intrusion of brackish water 

into the aquifer from the bordering estuary.

Water secured from marble formations is moderately to very hard. 

Soft water may be expected from the igneous and metamorphosed 

bedrocks and their overlying mantles. Some man-caused pollutants 

are discernible in most surface water and in some local supplies of 

ground water; detergents are widespread although usually in low 

concentrations. Storm-water runoff from developed areas contains 

many pollutants which vary in amount diurnally and seasonally; the

85
most noticeable are traceable to week-day activities associated with 

gas stations, stores, and households in general, and to the practice of 

salting slippery roads in winter.

Waste is disposed of through sanitary sewers in many sections of 

the basin adjacent to Baltimore; storm-water runoff i-^ conducted 

through a separate system. Joppatowne has a primary treatment 

plant. In the rest of the area, settlements and isolated homes are 

dependent upon septic tanks.

Erosion and sedimentation within the basin was a problem in the 

18th and 19th centuries; the silting of the port of Jopps is attributable to intensive farming upstream. At present (1964) the sediment 

erosion rate is low, except during the months or years wl ^n tracts of 

land are stripped for development; the two reservoirs have a life 

expectancy of almost 1,000 years.

Recreational facilities in the basin are now centered on Loch Raven 

and Prettyboy Reservoirs. The Baltimore City Bureau of Water 

Supply permits fishing from shores and from electric motorboats in 

areas well above the dams and maintains attractive picnic grounds 

and horseback and hiking trails.

Trends affecting the basin and plans concerning it indicate that 

more and more land will be used for housing developments, particularly in the sections below Prettyboy Dam. More wrter will be 

diverted to metropolitan mains. More roads and highways will 

traverse the drainage basin. An increasing number of motorists will 

seek recreation in the valley. The basin's population is expected to 

triple by the year 2010, at which time a quarter of a million people 

will live there. The intent of the Baltimore Regional Planning 

Council is to cluster most families in several planned communities 

small cities or metrotowns. Water from Gunpowder Falls will be 

drawn at a rate of 220 mgd, if officials of the Bureau of Water 

Supply decide to risk a deficiency in 1 year out of 10. The bureau 

now plans to use as much of the local purer and cheaper supply as 

possible before tapping water from the Susquehanna River through 

the pipeline now being constructed.

The entire basin has been zoned for industrial, commercial, residential, agricultural, and recreational sections or for open-space 

development, and extensions of the present road network have been 

planned for the coming 20 years. About 20,000 acres1 of valleybottom land (some of it in the Little Gunpowder Falls drainage 

basin to the east) and estuary shoreland are being acquired for a 

State park.

Increasing demands on the local resources are inevitable. Equitable adjustments among the competing interests will require an

86
understanding of the hydrologic system and the effects of alternative 

actions. This report has outlined some of the hydrologic effects of 

some alternatives that are presently under consideration by th? community and some that are not.

The need for living space can affect the maintenance of a drainage 

basin which has been developed for water supply. The prncipal 

effects of urbanization are (1) pollution of the storm-water runoff, 

and (2) temporary increases in sedimentation. Runoff from residential and commercial sections contains varying amounts of undesirable dissolved solids, seldom enough to cause alarm but enough to 

suggest that a planned community should not be placed upstream 

from a water-supply reservoir. Erosion from land surfaces that are 

being stripped during development will result in an increased rate of 

sedimentation in impoundments farther downstream in the rbsence 

of corrective action such as the construction of settling ponds

The competition between the uses of the basin for water and for 

recreation can be resolved by compromise and additional development:

1. In Loch Raven Reservoir if the water level could be maintained within 3 feet or less of the top of the dam, watersupply management could count on 190 mgd with r, probable deficiency in 1 year out of 10, and recreation seekers 

would be confronted only rarely with wide expanses of bare 

shoreline.

2. In the channel below Loch Raven Dam if 0.8 to 2.4 mgd 

could be released from the water supply during the warm 

dry periods of the year to assure a flow of 10 to 20 cfs 

downstream, the lower valley would be much more attractive, healthy, and useful for recreational purposes.

3. At Liberty Reservoir (Baltimore's source of water on the 

Patapsco River) a higher water level could be maintained, 

for aesthetic and practical purposes, if water shcTild be 

diverted as needed from Prettyboy Reservoir on th^ Gunpowder Falls. Apparently Prettyboy Reservoir will be 

subjected to increasingly frequent drawdowns to keep the 

water level in Loch Raven within 10 feet of the dam crest; 

some of its water could be diverted to augment the Liberty 

supply on the basis of management needs.

4. In the basin above Loch Raven Reservoir the construction 

of several relatively small impoundments on tributaries of 

the Gunpowder Falls above Loch Raven Reservoir would 

capture more water as well as provide more centers for 

fishermen, picnickers, and the like.

87
Although impounded water covers land that could be used for 

living space, the increasing need for recreation facilities utilizing 

bodies of water suggests that more small dams be constructed and 

lakes be made available within the Gunpowder Falls basin. Besides 

these lakes, a reservoir on State park land, in the adjacent Little 

Gunpowder Falls drainage basin but outside of the Metropolitan 

Baltimore water-supply basin, could be used for swimming, water 

skiing, and other sports not now permitted at the Bureau of Water 

Supply impoundments. Another way of alleviating future friction 

between living-space and recreation needs in the basin would be to 

expand present plans for the development of the tidal section of the 

State park land. Maryland has little public shoreline land, but more 

and more people will want to use local beaches and marinas. By 

locating facilities where they can be expanded and by securing permission to use some of the shoreline belonging to the nearby military 

base, development might keep pace with need for many years to 

come.

SELECTED REFERENCES

Alien, F. E., 1958, Study for a proposed Gunpowder River valley park system: 

Maryland Plan. Comm. Publ. 99, 26 p.

Baltimore City Bureau of Water Supply, 1962, Predicted water consumption in 

the Baltimore water service area for the years 1985 and 2010: The Bur. 

Analyzer Office, 17 p.

Baltimore County Agent's Office, 1960, Brief facts about agriculture in Baltimore County, Maryland: Baltimore County Agent's Office, 1 p.

Baltimore County Office of Planning and Zoning, 1962, Baltimore County population, based on final 1960 U.S. Census data: Baltimore County Office of 

Plan, and Zoning, 12 p.

Baltimore Regional Planning Council, Maryland State Planning Department, 

1962, Metrotowns for the Baltimore region: A pattern emerge-1 : Maryland 

State Plan. Dept. Plan. Rept. 2, 16 p.

 1963, Metrotowns for the Baltimore region: Stages an-'' measures: 

Maryland State Plan. Dept. Plan. Rept. 3, 16 p.

Bennett, R. R., and Meyer, R. R., 1952, Geology and ground water resources of 

the Baltimore area: Maryland Dept. Geology, Mines and Water Resources 

Bull. 4, 573 p.

Brune, G. M., 1953, Trap efficiency of reservoirs: Am. Geophys. Union Trails., 

v. 34, no. 3, p. 408-418.

Carter, R. W., 1961, Magnitude and frequency of floods in suburban areas: 

U.S. Geol. Survey Prof. Paper 424-B, p. B9-B11.

Dingman, R. ,L, and Ferguson, H. F., 1956, The water resources of Baltimore 

and Harford Counties: Maryland Dept. Geology, Mines an? Water Resources Bull. 17, 233 p.

Ferris, J. G., Knowles, D. B., Brown, R. H., and Stallman, R. W., 1962, Theory 

of aquifer tests: U.S. Geol. Survey Water-Supply Paper 1536-E, 174 p.

Geyer, J. C., 1959, Water supply and sewerage: Baltimore Regional Plan. 

Council, Maryland Plan. Comm. Tech. Rept. 4, 40 p.

88
Gottman, Jean, 1957, Megalopolis, or the urbanization of the northeastern seaboard : Econ. Geography, v. 33, p. 189-200.

Gottschalk, L. C., 1943, Report on the reconnaissance sedimentation surveys of 

Loch Raven and Prettyboy Reservoirs, Baltimore, Maryland: U.S. Dept. 

Agriculture Soil Conserv. Service Spec. Rept. 5, 21 p.

 1945, Effects of soil erosion on navigation in upper Chesapeake Bay: 

The Geog. Review, v. 35, no. 1, p. 219-238.

Gregory, J. H., Requardt, G. J., and Wolman, Abel, 1934, Report to tte Public 

Improvement Commission of the City of Baltimore on future sources of 

water supply and appurtenant problems: Advisory Engineers o^ Water 

Supply rept., 226 p.

Guy, H. P., and Ferguson, G. E., 1962, Sediment in small reservoirs due to 

urbanization: Am. Soc. Civil Engineers Proc., v. 88, no. HY2, pt. 1, p. 

27-37.

Hamilton, A. B., 1961, Comparative census of Maryland agriculture by counties: 

Maryland Univ. Extension Service Misc. Publ. 55, 52 p.

Haney, P. D., 1962, Report on waste-water collection and disposal in the Gunpowder River basin: Black and Veatch, Consulting Engineers re^»t., 45 p. 

(Prepared for Plan. Dept. of Maryland.)

Hardison, C. H., and Furness, L. W., 1963, Discussion of paper by J. B. Stall, 

Reservoir mass analysis by a low flow series: Am. Soc. Civil Engineers 

Proc., v. 89, no. SA2, p. 119-122.

Holeman, J. N., and Geiger, A. F., 1959, Sedimentation of Lake Barcroft, Fairfax County, Va.: U.S. Dept. of Agriculture Soil Conserv. Service Tech. 

Paper 136, 12 p.

Howard, G. W., 1873, The Monumental City, its past history and present resources : Baltimore, J. D. Ehlers and Co., v. 1 and 2, 352 p.

Langbein, W. B., 1958, Queuing theory and water storage: Am. Soc. Civil 

Engineers Proc., v. 84, no. HY5, pt. 1, p. 1811-7 1811-13.

Maryland State Planning Commission, 1959, Regional Land Use: Paltimore 

Regional Plan. Council Tech. Rept. 1, 73 p.

Maryland State Planning Department, 1961, Maryland population 1930-1960, 

by election districts, cities and towns: Publ. 113, 51 p.

 1962, Maryland County economic data book: Publ. 66 (4th rev.), p. 

12-13.

Maryland State Roads Commission and U.S. Department of Commerce, 1961. 

General highway map, 20 year needs: Plan, and Programming D'v. Maryland State Roads Comm. in cooperation with Bur. Public Roac's of the 

U.S. Dept. Commerce.

The Maryland-National Capital Park and Planning Commission, 1962, On 

wedges and corridors; a general plan for the Maryland-Washirgton Regional District: Baltimore, The Maryland-National Capital Park and Plan. 

Comm., 159 p.

Munson, W. C., 1962, Method for estimating consumptive use of vater for 

agriculture: Am. Soc. Civil Engineers Trans., v. 127, pt. 3, paper 3331, p. 

200-212.

Otton, E. G., Martin, R. O. R., and Durum, W. H., 1964, Water resources of the 

Baltimore area: U.S. Geol. Survey Water-Supply Paper 1499-F, 153 p.

Reigner, I. C., and Sushko, W. C., 1960, The Baltimore watershed, an example 

of good management: Public Works Mag., v. 91, no. 4, p. 85-8.S.

89
Requardt, G. J., Shaw, H. B., and Wolman, Abel, 1953, Report to the City of 

Baltimore on future sources of water supply and appurtenar*; problems: 

Board of Advisory Engineers on Future Water Supply Dept, 62 p.

Scharf, J. T., 1881, History of Baltimore City and County: Philadelphia, L. H. 

Everts Publishers, 947 p.

Seitz, M. A., 1946, The history of the Hoffman paper mills in Maryland: Baltimore, Holliday Press, 63 p.

ACKNOWLEDGMENTS

The authors greatly appreciate the help of hundreds of people, 

closely associated with the many complex aspects of Metropolitan 

Baltimore and with developments in the Gunpowder Falls basin, who 

contributed to our knowledge and influenced our thinking. We are 

especially indebted to members of the following State, county, and 

city agencies:

Technical Advisory Committee for the Maryland Water 

Supply and Eequirements Study, Maryland /State Planning 

Commission. jjf

Maryland State Planning Commission ami its adjunct, the 

Baltimore Eegional Planning Council.

Maryland State Roads Commission, especially the Planning 

and Programming Division.

Maryland Department of Forests and Parks.

Baltimore County Office of Planning and Zoning.

Baltimore County Department of Recreation.

Baltimore County Department of Public Works.

Baltimore City Bureau of Water Supply.

Baltimore City Bureau of Sewers.

Many colleagues in the Water Resources Division of the U.S. 

Geological Survey gave us technical assistance and guidance. Special 

mention should be made of Mr. C. H. Hardison's help with determinations of statistical probabilities, of Mr. E. S. Simpson's monitoring 

and interpretations of the test-well pumping at Joppatovaie. Past 

and present members of the Water Resources Division Council for 

the State of Maryland provided records and gave of their knowledge 

gained from experience.

We also thank Whitman, Requardt and Associates, Baltimore, for 

permitting us to participate in the pumping tests of wells at Joppatowne and for sharing the derived data with us.

90

US." GOVERNMENT PRINTING OFFICE : 1966 O 784-926