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TECHNICAL REFERENCE DOCUMENT

PROTECT AND MONITOR WATER RESOURCES

1. Introduction

The availability and quality of freshwater supplies for human and ecological needs are critical 

factors influencing the health and livelihoods of all people in the nation. Growth in human 

population and water use, degradation of water supplies by contamination, and recognition of the 

legitimate needs for freshwater in order to support critical ecosystem functions may lead to 

increasing scarcity and conflict over freshwater supplies in coming years. Water conflicts, which 

once were confined largely to the arid parts of the country, are now becoming increasingly 

common in the humid parts, as well. The potential for alterations in climate creates an even 

stronger need for reliable information about the status of freshwater resources. While this report is 

entitled “Protect and Monitor Water Resources”, this title actually reflects intermediate goals. The 

end goals toward which the efforts described in this chapter are directed are more clearly stated as 

“ensuring water availability and quality for both human and ecological needs, and minimizing 

conflicts over water resources.”

2. User Requirements

Informed resource management begins with accurate information on both supply and use of 

freshwater. The first step is basic measurements of the fluxes and storage of water in a watershed 

and its underlying aquifer system (Figure 1). 

Precipitation, streamflow, lake and reservoir storage, evaporation and transpiration, soil moisture, 

ground-water storage, ground-water recharge and discharge; and withdrawals for various uses 

should all be measured. Concentrations and loads of various significant natural and anthropogenic 

contaminants must also be measured to determine their impact on water availability and on aquatic 

habitats in freshwater, estuarine, and marine environments. Most of these measurements must be 

made using in situ sensors, sampling, and manual measurement techniques, but some can be done 

using remote sensing. Temporal variability and long-term trends in these measures of availability 

must be recorded and documented. This long-term, dense hydrologic database is needed in order 

for scientists, water managers and policy makers to make appropriate decisions regarding 

prediction of future conditions including floods and droughts, ground-water depletion, and 

reservoir storage. The data are also needed in order to develop accurate assessments and 

simulation tools to support decision-making related to the effects of alternative future water-use 

scenarios on water supplies, and the effects of various land- and chemical-use scenarios on the 

quality and quantity of freshwater resources. 
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Figure 1: The hydrologic cycle and estimates of storage and fluxes

3. Existing Capabilities and Commonalities

Observations for monitoring and protecting water resources are made by several Federal agencies. 

The observations include monitoring of fluxes and storage in the various components of the 

hydrologic cycle, and monitoring of chemical and biological characteristics of water resources. 

Monitoring systems include networks of manually operated observation stations and sampling 

sites, networks of in situ sensors, remote sensing systems, and modeling based on various 

combinations of all three. There are some examples of strong coordination and collaboration 

among agencies, but it is currently not possible to go to one single source for comprehensive 

water-resources monitoring information. Notable examples of water-resources monitoring 

programs are described below:

Precipitation

Precipitation quantity monitoring is done by NOAA using a combination of ground-based 

observation stations and remote sensing. The ground-based daily observation network comprises 

about 5,000 stations associated with the 13 River Forecast Centers and several hundred stations 

associated with the Climate Anomaly Database (http://www.cpc.ncep.noaa.gov/). These stations 

provide national coverage at a resolution of about 1⁄4 degree of latitude and longitude 

(http://www.cpc.noaa.gov/cgi-bin/station_realtime.sh).
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A typical product from the precipitation monitoring network is the 24-hour precipitation quantity 

map: (http://www.cpc.noaa.gov/products/precip/realtime/us_precip.html).

NOAA also makes available on its web site high-resolution radar data from the national network 

of Next Generation Radar (NEXRAD) is now available in real time to government, university and 

private sector users. NEXRAD data are used in quality control of the ground-based monitoring 

data (http://www.roc.noaa.gov/reflect.asp).

For global precipitation monitoring, NOAA’s Global Precipitation Climatology Project in the 

Climate Prediction Center collects precipitation quantity data from ground-based networks 

worldwide, and also uses remote sensing to estimate precipitation for the globe.

Snow

Snowfall is of particular interest to water-resources managers because of the seasonal storage of 

water in the snowpack. NOAA’s National Operational Hydrologic Remote Sensing Center 

(NOHRSC) provides remotely-sensed and modeled hydrology products for the conterminous U.S. 

and Alaska. The NOHRSC national and regional snow analyses provide a daily synoptic overview 

of snow conditions for the conterminous U.S. as well as for the 18 U.S. snow regions at a higher 

resolution. The snow analyses are text descriptions of daily snow accumulation based on snow 

observations and modeled snowpack characteristics. They review both the meteorological 

observations of snowfall and snow on the ground as well as the snowfall and snow accumulation 

simulated by the NOHRSC snow model. Unique snow data observations such as airborne snow 

water equivalent estimates are reviewed in the text product during the course of operational 

airborne snow survey missions. Image maps of snow characteristics and other graphics 

summaries are hyper-linked in the analyses to highlight specific points of interest. The snow 

analyses are prepared each weekday by NOHRSC personnel. Snowfall maps are available for the 

most recent 1, 2, 3 and 7-day period by state or for the entire nation. Also available are current 

snow depth maps (http://lwf.ncdc.noaa.gov/oa/climate/research/snow/recent.html), snow water 

equivalent maps (http://www.nohrsc.nws.gov/nsa/), and snowmelt maps 

(http://www.nohrsc.nws.gov/nsa/). NOAA also disseminates national maps of recent snowfall and 

snow depth: (http://lwf.ncdc.noaa.gov/oa/climate/research/snow/recent.html).

The Natural Resources Conservation Service (NRCS) National Water and Climate Center installs, 

operates, and maintains an extensive, automated system to collect snowpack and related climatic 

data in the Western United States called SNOTEL (for SNOwpack TELemetry) 

(http://www.wcc.nrcs.usda.gov/about/nwcc-function.html); photo of snowtel station 

(http://www.wcc.nrcs.usda.gov/snow/). The system evolved from NRCS's Congressional mandate 

in the mid-1930's "to measure snowpack in the mountains of the West and forecast the water 

supply." The programs began with manual measurements of snow courses; since 1980, SNOTEL 

has used telemetered data from 600 automated sensors in 11 western states including Alaska.

SNOTEL uses meteor burst communications technology to collect and communicate data in nearreal-time. VHF radio signals are reflected at a steep angle off the ever present band of ionized 

meteorites existing from about 50 to 75 miles above the Earth. Satellites are not involved; NRCS 

operates and controls the entire system. The sites are generally located in remote high-mountain 
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watersheds where access is often difficult or restricted. Access for maintenance by NRCS includes 

various modes from hiking and skiing to helicopters. For example, to see the distribution of 

SNOTEL sites in Wyoming, visit http://www.wcc.nrcs.usda.gov/snotel/Wyoming/wyoming.html. 

For an annual graph of snowpack data from USDA SNOTEL site in Wyoming showing departure 

from normal precipitation and snow water equivalent, visit http://www.wcc.nrcs.usda.gov. For a 

map of the mountain snowpack of the western U.S. as monitored by USDA NRCS SNOTEL 

network, visit ftp://ftp.wcc.nrcs.usda.gov/downloads/wsf/jan04wsfwww.pdf.

Precipitation Quality

The National Atmospheric Deposition Program coordinates an interagency network of 250 

precipitation quality monitoring stations to monitor the acidity of precipitation as well as other 

constituents such as nitrates, sulfates, and ammonia (http://bqs.usgs.gov/acidrain/). Annually the 

data are disseminated in several forms, including national maps: 

(http://nadp.sws.uiuc.edu/isopleths/maps2002/phlab.gif).

Streamflow

The U.S. Geological Survey (USGS) operates a national network of about 7,000 telemetered 

streamgages (http://waterdata.usgs.gov/nwis/rt, http://water.usgs.gov/nsip/. The network is 

supported jointly with other federal, state, and local governments. The number of gages in the 

network has been declining slightly in recent years as federal and state budgets have become 

tighter. The data are collected by automated water-level sensors and converted to streamflow 

according to empirical stage-discharge relations deve loped for each site. The stage-discharge 

relations are developed based on manual discharge measurements made about 8 times per year at 

each station. Automated water-level data are telemetered, generally using the GOES satellites, 

and are disseminated on the internet (http://waterdata.usgs.gov/nwis/rt).

Surface Water Quality

There are numerous federal, regional, state, tribal, and local monitoring programs for ambient 

surface water quality conditions and compliance monitoring 

(http://www.epa.gov/ebtpages/watewaterqualitymonitoring.html). Most of these data are input to 

EPA’s Storage and Retrieval (STORET) database (http://www.epa.gov/storet/). EPA summarizes 

state and federal water-quality data annually in a national report on stream water quality. This

National Water Quality Inventory Report to Congress (305(b) report) (http://www.epa.gov/305b/) 

is the primary vehicle for informing Congress and the public about general water quality 

conditions in the United States. This document characterizes our water quality, identifies 

widespread water quality problems of national significance, and describes various programs 

implemented to restore and protect our waters. It characterizes the following water body types as 

“good”, “threatened”, or “impaired”, based on sampling results submitted by the states’ rivers, 

streams, creeks, lakes, ponds, reservoirs, bays, estuaries and wetlands, coastal waters, ocean and 

near coastal waters. (http://oaspub.epa.gov/waters/w305b_report.nation).

The USGS conducts a nationwide monitoring and assessment program called the National Water 

Quality Assessment that includes a network of 6,100 stream-quality monitoring sites. 

(http://water.usgs.gov/nawqa/). Samples are analyzed for a wide variety of nutrients, pesticides, 

volatile organic compounds, metals, and biological indicators, and are compared with land-use 
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data. Customized national maps of NAWQA data are available at 

http://water.usgs.gov/nawqa/data. The USGS SPARROW water-quality model uses observed 

water-quality data and a va riety of basin characteristics to estimate concentrations and loads of 

several constituents nationwide, including unmonitored streams. For example, to see a map of 

model-estimated yields of nitrate-nitrogen from U.S. river basins estimated by the USGS 

SPARROW model based on water-quality sampling and basin characteristics, please visit 

http://water.usgs.gov/nawqa/sparrow/. Units are kg/square km/yr.

Another large-scale USGS stream monitoring program is the National Stream Quality Accounting 

Network (NASQAN), which routinely monitors stations on the nation’s largest rivers, the 

Mississippi (including the Missouri and Ohio), the Columbia, the Colorado, the Rio Grande, and 

the Yukon. The Benchmark network monitors 48 stations on smaller, relatively pristine streams 

nationwide, and the Toxic Substances Hydrology Program includes more experimental monitoring 

of selected sites nationwide for organic wastewater contaminants including pharmaceuticals and 

endocrine-disrupting compounds. All USGS water-quality and water quantity data are stored in 

the National Water Information System (http://water.usgs.gov/nwis).

Water-quality data from both the EPA STORET database and the USGS National Water 

Information System can be accessed through a convenient single portal called “Window to My 

Environment” (http://www.epa.gov/enviro/wme/).

An important water-quality parameter that is a controlling factor for many total maximum daily 

load allocations as well as for determining the useful lifespan of many dams and reservoirs is 

suspended sediment. The USGS and several cooperating agencies have developed a suspended 

sediment database that provides daily concentrations and loads of sediment at many locations 

around the nation, plus ancillary data (http://water.usgs.gov/osw/suspended_sediment/index.html).

Monitoring of lake and reservoir water quality was formerly coordinated and funded under the 

Clean Lakes Program (http://www.epa.gov/owow/lakes/cllkspgm.html) but no appropriations have 

been made since 1994. Some lake monitoring is encouraged under the implementation of section 

319 of the Clean Water Act. Additional monitoring is done by reservoir management agencies 

such as TVA, the Corps of Engineers, and the Bureau of Reclamation; and by the USGS, 

academic institutions, and other entities.

Lake and Reservoir Storage

Some of these data are included in the USGS National Water Information System 

(water.usgs.gov/nwis) as water-level data. Storage data are collected for individual projects by 

reservoir management agencies, typically using automated SCADA systems, but are not collected 

and reported on a national basis.

Evaporation and Transpiration

NOAA collects and disseminates nationwide evaporation data based on observations at weather 

stations equipped with evaporation pans (http://www.cpc.noaa.gov/products/soilmst/e.html). 

Some excellent academic and government studies of evaporation and transpiration are underway 

in selected areas. 
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Soil Moisture

For nationwide assessment and prediction purposes, soil moisture is estimated by a one-layer 

hydrological model using observed precipitation and temperature 

(http://www.cpc.noaa.gov/products/soilmst). A series of maps showing most recent day, monthly 

and 12 months calculated soil moisture, anomalies and percentiles have been archived 

(http://www.cpc.ncep.noaa.gov/soilmst/w.html).

A more sophisticated soil moisture product is the four-layer soil moisture estimate calculated in 

the Land Data Assimilation System (LDAS), based upon the NOAH four-layer land surface 

model. The North American LDAS is produced in real time at NOAA’s National Center for 

Environmental Prediction, in collaboration with NASA and university partners 

(http://ldas.gsfc.nasa.gov). LDAS will lead to more accurate reanalysis and forecast simulations 

by numerical weather prediction (NWP) models, which typically have large errors in stores of soil 

moisture and energy and in turn, degrade the accuracy of forecasts. 

Some additional promising experiments are underway by NASA and USDA to monitor soil 

moisture using satellites (http://hydrolab.arsusda.gov/smex03/). The NASA Aqua and Japanese 

ADEOS-II Advanced Microwave Scanning Radiometer Programs are working toward developing 

and providing daily soil moisture products.

The USDA Natural Resources Conservation Service also monitors soil moisture as part of their 

Soil Moisture/Soil Temperature Pilot project (SM/STPP), and disseminates a limited set of soil 

moisture data for the U.S. via the Soil Climate Analysis Network 

(http://www.wcc.nrcs.usda.gov/scan/).

Ground Water Storage

The USGS maintains a network of wells to monitor the effects of droughts and other climate 

variability on ground-water levels. The network consists of a national network of about 150 wells. 

Some of these have real-time telemetry, some have continuous records obtained periodically 

during field visits, and some have periodic manual measurements 

(http://groundwaterwatch.usgs.gov).

There are many thousands of monitoring wells that are measured by a variety of federal, state, 

local, and tribal agencies, but there is little coordination of the monitoring programs. In 2002 

there were about 42,000 long-term observation wells in the U.S. with 5 or more years of record 

(http://water.usgs.gov/pubs/circ/circ1223/). Some aquifers have extensive ground-water-level 

trend data, some have little. One example of a well-monitored major aquifer is the High Plains 

Aquifer, in which water levels in 7,000 wells are measured annually 

(http://water.usgs.gov/wid/FS_215-95/FS_215-95.html).

Another good example of ground-water level monitoring is the Pennsylvania ground water 

network, which provides on-line maps and graphs of ground-water levels for every county in the 

state: (http://pa.water.usgs.gov/monitor/gw/index.html).
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Drought Monitoring

The National Drought Mitigation Center at the University of Nebraska 

(http://drought.unl.edu/dm/), in cooperation with NOAA, USDA, and other agencies, assembles 

drought-related data from many sources and provides them on a single web site. There are good 

efforts underway to extend this drought monitoring to cover all of North America. Several data 

products are provided, along with a combined drought monitor map for the U.S. 

(http://www.drought.unl.edu/dm/monitor.html). Additional combinations of indicator variables 

should be considered for drought monitoring, including, for example, rangeland condition.

NOAA has developed a plan, endorsed by the Western Governors Association, for a National 

Integrated Drought Information System that would provide enhanced monitoring capabilities, 

greater integration of data related to droughts, and enhanced forecasting capabilities. The plan is 

available at http://www.westgov.org/wga/publicat/nidis.pdf.

Ground Water Quality

Monitoring of ground-water quality is spotty. Most states have programs for ambient groundwater quality monitoring, but they are not coordinated as a national network. The USGS National 

Water Quality Assessment (NAWQA), which includes ground water, has water-quality data from 

7,000 wells in its data warehouse (water.usgs.gov/nawqa/data).

Ground-Water Recharge and Discharge

These important components of the hydrologic cycle are usually estimated rather than measured 

directly. Availability and reliability of estimates varies greatly among U.S. aquifers. One 

example of a recent study with good estimates of recharge and discharge is a USGS study of the 

Middle Rio Grande aquifer system in the vicinity of Albuquerque, NM 

(http://water.usgs.gov/pubs/circ/2002/circ1222/).

Water Use

States and Federal agencies cooperate, with varying levels of effort, on measuring and estimating 

water use in various categories, resulting in national reports every 5 years 

(http://www.usgs.gov/features/wateruse.html). The most recent national compilation is an on-line 

report entitled “Estimated Use of Water in the United States in 2000” 

(http://water.usgs.gov/pubs/circ/2004/circ1268/)

The water use data compilation is a useful tool, but it has limitations. Data are reported only every 

5 years. Data are collected at the county level, but are aggregated at the state level in the national 

report. Some water-use categories, such as irrigation and domestic supply, must be estimated 

because no accurate monitoring is done. There is a need for better monitoring of consumptive 

water use, which includes uses that do not return water to the surface or ground-water flow 

systems.

Drinking Water

The U.S. Environmental Protection Agency maintains several databases with nationwide 

information about drinking-water systems. The Safe Drinking Water Information System

(SDWIS/FED) (http://www.epa.gov/safewater/sdwisfed/about_fed.html) contains data about 

locations and characteristics of the Nation’s public drinking water systems, and about violations of 
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drinking-water standards or protocols. SDWIS/FED stores the information EPA needs to monitor 

approximately 175,000 public water systems. 

States supervise the drinking water systems within their jurisdictions to ensure that each public 

water system meets state and EPA standards for safe drinking water. The Safe Drinking Water Act 

(SDWA) requires states to report drinking water information periodically to EPA; this information 

is maintained in SDWIS/FED. States report the following information to EPA:

• Basic information on each water system, including: name, ID number, number of 

people served, type of system (year-round or seasonal), and source of water 

(ground water or surface water) 

• Violation information for each water system: whether it has followed established 

monitoring and reporting schedules, complied with mandated treatment techniques, 

or violated any Maximum Contaminant Levels (MCLs) 

• Enforcement information: what actions states have taken to ensure that drinking 

water systems return to compliance if they are in violation of a drinking water 

regulation 

• Sampling results for unregulated contaminants and for regulated contaminants 

when the monitoring results exceed the MCL 

Currently, EPA is in the process of determining additional information states may be required to 

report in the future, such as the city and county where the system is located (most states already 

report this information), and the latitude/longitude of the source water intake. 

EPA and USGS have collaborated on recent improvements in the locational data in SDWIS/FED, 

such that now accurate locations are available for all surface-water intakes and ground-water wells 

used for public supply. Due to the sensitive nature of the data, this database is not made available 

publicly.

For data on concentrations of contaminants in drinking water, EPA maintains a National 

Contaminant Occurrence Database (NCOD) (http://www.epa.gov/safewater/data/ncod.html). 

NCOD provides a library of water sample analytical data (or “samples data”) that EPA is currently 

using and has used in the past for analysis, rulemaking, and rule evaluation. The drinking water 

sample data, collected at Public Water Systems, are for both regulated and unregulated 

contaminants. The data have been extensively checked for data quality and analyzed for national 

representativeness.

Within its National Water Quality Assessment Program, the USGS maintains a database of water 

quality data from domestic wells. Domestic wells are not regulated by EPA and do not contribute 

data to the EPA databases.

Land Use and Impervious Area
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The way we use our land has a significant impact on our water resources. For that reason, spatial 

databases covering certain aspects of land use are of great importance in understanding, 

protecting, and predicting the quantity and quality of our water resources. The amounts and types 

of crops we grow, the extent of irrigated land, the types of best-management practices employed to 

protect watersheds, various practices related to forestry, mining, grazing, and urbanization all 

affect water resources. Of particular interest is the extent of impervious or paved area in any given 

watershed, since impervious area retards infiltration and contributes to quicker runoff and higher 

storm peak flows in streams. These land-use characteristics can be monitored with various remote 

sensing systems such as Landsat and Modis. 

Wetlands

Wetlands are an important component of the hydrologic system, both biologically and 

hydrologically. They are monitored through the National Wetlands Inventory 

(http://wetlands.fws.gov), a program of the U.S. Fish and Wildlife Service. Wetland maps, 

developed through a combination of remotes sensing and ground-truth, are available in a number 

of formats. 

National Hydrography Dataset

An important commonality of all of the surface-water related data mentioned above is the 

association of specific data with a specific stream reach in a network where flow relationships 

(upstream and downstream) are known. This spatial information is the core of the National 

Hydrography Dataset (NHD), a collaboration of EPA and USGS. NHD is a digital depiction of 

the stream reach network of the entire country, with each reach connected to the network in such a 

way that flow relationships are known. In many cases, point data mentioned above are associated 

with individual stream reaches in the NHD. In other cases, this association has yet to be made. 

The NHD is the key to linking surface water data with other geospatial coverages important to 

hydrology, such as digital elevation models (which help to describe drainage area boundaries and 

stream slopes), watershed boundaries, land cover and land use, and impervious area.

Synthesis of Hydrologic Information

Some synthesis of hydrologic datasets has been done at the National Weather Service Hydrologic 

Information Center (http://www.nws.noaa.gov/oh/hic/conds.shtml), the NWS Climate Prediction 

Center (http://www.cpc.ncep.noaa.gov/products/MD_index.html), the NOAA National Climatic 

Data Center (http://www.ncdc.noaa.gov/oa/climate/research/monitoring.html), and the National 

Drought Mitigation Center (http://www.drought.unl.edu/dm/current.html). A significant 

additional effort is underway as a collaboration among NOAA, the Drought Mitigation Center, 

NRCS, and USGS. This effort, involving a new website that will be called “Watermonitor.gov”, 

will combine water quantity information on streamflow, reservoir storage, ground-water storage, 

and snowpack storage, and will provide forecasts and links for further information. The USGS, 

through its Water Information Coordination Program (http://water.usgs.gov/wicp/aboutus.html), 

plays a strong coordinating role among federal and other government agencies involved in water 

information collection and dissemination. This role is supported by external advice from a Federal 

Advisory Committee Act group called the Advisory Committee on Water Information (ACWI), 

comprising representatives from Federal, state, local, and tribal governments, NGO’s, and the 

private sector. As noted above, EPA collects water-quality data from many different sources in its 
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STORET database, and EPA and USGS collaborate on Window to My Environment to provide a 

common portal to STORET and the USGS National Water Information System.

The U.S. Forest Service, which has a long history of programs to protect and manage water 

resources, has a Natural Resources Inventory System that has a significant component related to 

water (http://www.fs.fed.us/emc/nris/water/). This component focuses on data that describes 

aquatic habitats and stream morphology, watershed characteristics, water rights and uses, and 

aquatic organisms.

This system is heavily oriented toward geospatial information, including the National 

Hydrographic Dataset. The WATER Team has been chartered by the Natural Resources 

Information System directors to steward the WATER module - an ORACLE database and user 

toolset application with GIS connections. The WATER application is designed to implement 

corporate data standards and promote integrated management of aquatic resource information, 

including maps and related data about stream and lake systems plus water improvements and 

rights. This information can be analyzed and presented at multiple geographic scales, both within 

and across administrative and jurisdictional boundaries.

There is a significant effort underway in the academic community, in association with the National 

Science Foundation, to enhance collection and integration of hydrologic data. The Consortium of 

Universities for the Advancement of Hydrologic Science, Inc. (CUAHSI) seeks to advance 

hydrologic science in the 21st century through a broad based program of observations and 

research., CUAHSI (http://www.cuahsi.org) has evolved a science and implementation plan 

through a series of workshops, meetings, and other collaborative exercises. A primary purpose of 

CUAHSI is to help develop basic programs and infrastructure to support community research. The 

infrastructure elements include a system of hydrologic observatories, a hydrologic information 

system, a hydrologic measurement technology facility, and a hydrologic synthesis center. 

The Sustainable Water Resources Roundtable (SWRRT) 

(http://water.usgs.gov/wicp/acwi/swrr/Rpt_Pubs/index.html) is a multi-agency organization 

aligned with other sustainable natural resources roundtables in an effort to define criteria and 

indicators that will enable us to monitor progress toward improving the sustainability of water 

resources. The SWRR criteria for sustainability of water resources, still a work in progress, are:

1. Ecological System. 

• Capacity to make water of appropriate quality & quantity available to support 

ecosystems

• Integrity of ecosystems 

2. Social System

• Social well-being resulting from use of water resources

• Social well-being resulting from use of water-related ecological resources
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• Legal, institutional, community and technical capacities for management of water 

and related land resources for sustainability.

3. Economic System

• Capacity to make water of appropriate quality and quantity available for human 

uses

• Economic well-being resulting from use of water related land resources

• Economic well-being resulting from use of water- related ecological resources

The Heinz Center for Science, Economics, and the Environment released a comprehensive report 

entitled The State of the Nation’s Ecosystems in 2002 (http://www.heinzctr.org/ecosystems/), with 

an update in 2003, and a follow-up report expected in 2007. Among the core national indicators 

are at least three related to water: water withdrawals, movement of nitrogen, and chemical 

contamination. The section on freshwater indicators 

(http://www.heinzctr.org/ecosystems/fr_water/indicators.shtml) lists 15 additional indicators 

specifically for the determination of the status of freshwater resources. These fall into categories 

of system dimensions, chemical and physical conditions, biological components, and human uses. 

According to the 2002 report, only 3 of the 15 indicators currently have “all necessary data 

available”: streamflow, water withdrawals, and waterborne disease outbreaks. (Arguments could 

reasonably be made that the data for these three indicators is not totally sufficient.) Seven of the 

indicators have “partial data available”, and the other five have “data not adequate for national 

reporting”.

In December 2002, the White House Council on Environmental Quality (CEQ) launched a new 

effort to enhance coordination among federal agencies and to develop policy guidance on the 

future development of environmental and sustainable development indicators. The CEQ working 

group will: 

• Develop agreement around a set of national-level environmental indicators that can 

be linked to regional and local conditions.

• Explore opportunities for collaboration among and between federal agencies, state, 

regional, and local agencies, nongovernmental organizations, and private-sector 

groups to improve the validity, reliability, consistency, and coverage of the data 

used for indicators.

• Consider how statistical reporting and data collection should be organized within 

the federal government, recognizing the data needs of agencies’ programs and 

statutory authorities. 

The goal of this effort is to have interlocking sets of environmental and human health indicators 

that can inform decisions at the local, state, regional, and national levels. Some of these indicators 

will relate to freshwater.
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Crosswalk with Other Focus Areas

Some of the observables associated with water monitoring and protection may also covered under 

other IWGEO focus areas, and other chapters in section (4). This crosswalk is summarized in 

Table 1:

Observable Disaster Ocean Climate Ag/Lan

d

Health Ecosystem Water

Precipitation x x x

Snow x x x

Precipitation quality x x x

Streamflow x x x x x

Surface water quality x x x x

Lake & reservoir storage x x x x x

Evaporation & 

transpiration

x x

Soil moisture x x x

Ground water storage x x x

Ground water quality x x x

Drought x x x x x x x

Water use x x x

Drinking water x x

Land use x x x x

Impervious area x x x

Wetlands x x x

National Hydrography 

Dataset

x x x x

Table 1: Related Societal Benefits
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4. Major Gaps and Challenges

Many of the pieces for holistic monitoring of the nation’s water resources are in place, but 

significant additional effort is needed to pull the programs together into a single coherent picture.

Table 2: Summary of Importance and Status of Water-Related Observables

Observable Observed 

or Derived

Amenable 

to Remote 

Sensing?

Importance Status Gaps and Challenges

Precipitation Observed Yes Important flux 

variable in the 

water cycle

Good national 

coverage with 

manual observing 

stations and radar 

networks

Need more real-time 

ground-based data for 

quantification. 

Preservation of longterm stations and their 

records. Need more 

stations on Tribal lands.

Snow Observed: 

depth, cover 

Derived: 

water 

equivalent, 

melt rate

Yes Important flux 

and storage 

variable; 

determines 

water supply for 

much of the 

West

Good national 

coverage from 

remote sensing and 

ground-based 

networks; some 

erosion of coverage 

of ground-based 

networks.

Maintain and expand 

coverage of SNOTEL 

stations. Expand 

coverage to the 

snowpack in the north 

central and 

northeastern states. 

Integrate in situ and 

remotely sensed data. 

Ground-truth snowmelt 

simulations. 

Precipitation 

quality

Observed No Monitors acid 

rain and 

deposition of 

nitrate, sulfate, 

ammonia from 

airborne 

sources

Good national 

coverage through 

cooperative groundbased network; need 

to maintain 

coverage.

Maintain and expand 

network.

Streamflow Observed: 

water level 

Derived: 

streamflow

Remote 

sensing may 

provide 

estimates for 

large 

ungaged 

rivers.

Important flux 

variable in the 

water cycle

Good national 

coverage through 

ground-based 

network; some 

erosion of coverage 

is occurring.

Currently the national 

network is funded 43% 

by state and local 

governments. 

Additional Federal 

funding is needed to 

maintain and expand 

the network. Research 

is needed on new noncontact and remotely 

sensed techniques for 

measuring streamflow.
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Observable Observed 

or Derived

Amenable 

to Remote 

Sensing?

Importance Status Gaps and Challenges

Surface water 

quality

Observed Remote 

sensing can 

monitor 

plumes of 

sediment 

and algae.

Needed to 

understand 

watershed 

processes and 

guide antipollution efforts.

Many entities collect 

data; national 

networks are 

somewhat limited 

and could be better 

linked.

Enhance spatial, 

temporal, and 

parameter coverage. 

Develop new in situ and 

remote sensors for 

water quality. Integrate 

data from wide variety 

of sources. Improve 

data comparability.

Lake & 

reservoir 

storage

Observed: 

water level 

Derived: 

contents

Remote 

sensing can 

determine 

areal extent 

of water 

surface.

Important 

storage variable 

in the water 

cycle

Many reservoir 

operators collect the 

data; national 

coverage should be 

improved.

Integrate data from 

various sources.

Evaporation & 

transpiration

Derived Can help 

with derived 

estimates.

Important flux 

variable in the 

water cycle.

National coverage 

could be improved.

Improve estimates. 

Improve spatial 

coverage of data to 

support estimates.

Soil moisture Observed 

and derived

Can help 

with derived 

estimates.

Important 

storage variable 

in the water 

cycle.

National coverage 

could be improved.

Enhance spatial 

coverage of in situ 

network. Integrate 

remote and in situ data.

Ground water 

storage

Observed: 

water level 

Derived: 

storage

Can help 

with 

measuring 

subsidence 

caused by 

GW 

withdrawal; 

may 

estimate 

saturated 

thickness.

Important 

storage variable 

in the water 

cycle.

Some aquifers well 

monitored; most 

could use 

improvement.

Enhance spatial and 

temporal coverage of 

ground-water level 

monitoring.

Ground water 

quality

Observed No Needed to 

understand 

aquifer 

processes and 

guide antipollution efforts.

Some national 

coverage but most 

efforts are local and 

not well linked.

Enhance spatial, 

temporal, and 

parameter coverage. 

Integrate data from 

various sources.
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Observable Observed 

or Derived

Amenable 

to Remote 

Sensing?

Importance Status Gaps and Challenges

Drought Derived Yes Needed to 

guide watersupply 

decisions and 

conservation 

efforts.

Good collaborations 

exist that integrate 

available data; some 

improvements 

possible.

Need research on 

better combinations of 

indicator parameters. 

Better coverage of 

some indicator 

parameters. Better 

integration of data from 

various sources. Need 

funding for NIDIS.

Water use Observed 

and derived

Can monitor 

extent of 

irrigated 

farmland.

Important flux 

variable in the 

water cycle.

Good coverage for 

some categories; 

estimates in others, 

better temporal 

reporting needed, 

better monitoring of 

consumptive use 

needed.

More precise estimates 

of certain uses, e.g., 

irrigation. Need better 

temporal resolution and 

better monitoring of 

consumptive uses.

Drinking water Observed 

and derived

No Needed for 

linking water 

and human 

health.

Good locational data 

available (not 

publicly), some good 

national datasets on 

compliance and 

contaminants.

Better spatial, temporal, 

and parameter 

coverage. Better 

integration of data from 

various sources. 

Land use Observed 

and derived

Yes Needed to 

understand and 

predict the links 

between land 

use and water.

Good national 

coverages available; 

need to be linked to 

watersheds.

Provide land-use/landcover data specific to a 

given watershed. Need 

better understanding of 

links between land use 

and water quality and 

quantity.

Impervious 

area

Derived Yes Determines 

whether water 

infiltrates or 

runs off.

Could be derived 

from remote sensing; 

not currently 

available nationwide.

Derive better and more 

up-to-date estimates of 

impervious area for a 

given watershed.

Wetlands Observed Yes Describes 

important 

ecosystem for 

hydrology and 

water quality.

Good national 

coverage.

Maintain and enhance 

coverage.

National 

Hydrography 

Dataset

Derived (not 

actually an 

observable; 

more like a 

partnership 

or a tool)

Yes Provides 

common spatial 

representation 

of all surface 

water data; 

could serve as 

the basis for an 

integrated 

system.

Good national 

coverage; needs 

some improvements.

Complete national 

coverage at the 

1:24,000 scale. Take 

care of edge-matching 

issues. Associate 

stream reaches with 

other water-related 

data.
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5. Future Earth Observation Systems that May Fill Gaps

For some observables, such as lake and reservoir quality, transpiration, ground-water storage, 

ground-water quality, ground-water recharge and discharge, and water use, improved data 

collection efforts are needed. For example, in monitoring water use, we do a fairly poor job of 

accounting for consumptive water use. We should account for all the water that falls as 

precipitation, evaporates, percolates to ground water, or runs off into the stream network, and then 

follow that water through the natural hydrologic cycle, as well as track all the human 

modifications to the natural cycle. We should be able to answer “how much?” and “where?” for 

all these processes. We currently don’t have a very complete or integrated accounting for human 

water withdrawals and consumptive use, and what we have is not collected on a frequent time 

scale. Much of this information is collected by irrigation companies and farmers, but there is little 

effort to collect and assemble the data.

For other observables, such as streamflow, stream water quality, and snowpack depth and water 

equivalent, good monitoring programs are in place but efforts are needed to prevent the loss of 

monitoring stations and enhance geographic coverage. Coverage of all the water-related 

observables in Indian Country should be enhanced. 

Extension of monitoring efforts to relevant worldwide monitoring is needed to provide the global 

context in which the nation’s resources fit. International water data are important not just to those 

in foreign countries, but also to many in this country. For example, American farmers are keenly 

interested in weather and water conditions in similar farming areas in other parts of the world. 

Much of the international water data collection effort is being coordinated under the Global 

Energy and Water Cycle Experiment (GEWEX). This is a program initiated by the World Climate 

Research Programme (WCRP) to observe, understand and model the hydrological cycle and 

energy fluxes in the atmosphere, at land surface and in the upper oceans. GEWEX is an integrated 

program of research, observations, and science activities ultimately leading to the prediction of 

global and regional climate change. The International GEWEX Project Office (IGPO) is the focal 

point for the planning and implementation of all GEWEX Projects and activities. 

GEWEX is conducted as part of the Integrated Global Observing Strategy 

(http://www.igospartners.org/). The Integrated Global Observing Strategy (IGOS) seeks to 

provide a comprehensive framework to harmonize the common interests of the major space-based 

and in situ systems for global observation of the Earth. It is being developed as an over-arching 

strategy for conducting observations relating to climate and atmosphere, oceans and coasts, the 

land surface and the Earth's interior. IGOS strives to build upon the strategies of existing 

international global observing programs, and upon current achievements. It seeks to improve 

observing capacity and deliver observations in a cost-effective and timely fashion. Additional 

efforts will be directed to those areas where satisfactory international arrangements and structures 

do not currently exist. IGOS is a strategic planning process, involving a number of partners, that 

links research, long-term monitoring and operational programs, as well as data producers and 

users, in a structure that helps determine observation gaps and identify the resources to fill 

observation needs. One part of the IGOS program, the Integrated Global Water Cycle 
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Observations (IGWCO) theme, is needed to provide monitoring data and contribute to improved 

predictions for variables such as precipitation, soil moisture and runoff over many times scales and 

spatial scales from local to global. IGWCO is also needed to address several critical science 

questions regarding the role of the water and energy cycle in maintaining the stability of the 

Earth’s climate system, feedback processes involving clouds and land surfaces that influence 

regional and global climate change, and the availability of fresh water resources.

The observations required to advance our understanding and modeling of these and other science 

questions cannot be adequately addressed through continued reliance on ad hoc observing 

systems. In August 2002, the World Summit for Sustainable Development (WSSD) in 

Johannesburg recognized the paramount importance of water issues and encouraged supporting 

global observations for improved understanding of the global water cycle. The Water Cycle 

Theme will be built on the experience of projects, such as the WCRP’s Global Energy and Water 

Cycle Experiment (GEWEX), that deal with the development of global data sets for clouds, 

precipitation and other important water-cycle variables such as soil moisture,

evaporation/evapotranspiration, energy and radiation budget parameters, among others.

As has been shown in some of the above sections, remote sensing can be an effective 

observational tool for many types of hydrologic measurements. Continuing research and groundtruth is needed to develop and refine remote-sensing tools for use in hydrologic observations. For 

example, the National Aeronautics and Space Administration (NASA) has an Earth Science 
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Enterprise program on Water and Energy Cycles (http://watercycle.gsfc.nasa.gov) that seeks to use 

advanced remote sensing to support improved hydrologic predictions. The aim is to 

improve/nurture the following global measurements: precipitation (P), evaporation (E), P-E and 

the land hydrologic state, such as soil-water, freeze/thaw and snow. NASA is exploring an 

integrating water-cycle mission which would observe water molecules through the atmosphere and 

land surface using an active/passing hyperspectral microwave instrument. There is a need to 

develop a greater understanding of the capacity of remote sensing to contribute to the 

observational database for water, and to prioritize the various satellites and sensors under 

consideration for development.

NASA’s Earth Observing System (EOS) Science Plan (http://eos.nasa.gov) contains major 

sections on observing and modeling hydrologic processes using remote sensing.

As with all the Earth-observing systems, there is a need to integrate data pertaining strictly to 

water with data pertaining to the interactions of humans with water and with their natural 

environment. Some of these data are best collected by social and economic scientists, but they 

must be integrated with the data discussed in this subchapter to provide a broad understanding of 

the issues surrounding water and its uses.

The 1995 Final Report of the Intergovernmental Task Force of Monitoring Water Quality (the 

forerunner to the current National Water Quality Monitoring Council under the Advisory 

Committee on Water Information) lists several suggestions for improving and integrating water 

quality monitoring data in its Major Conclusions and Recommendations 

(http://water.usgs.gov/wicp/itfm.html). Among the conclusions: 

• Tens of thousands of public and private organizations monitor water quality for a 

wide variety of objectives.

• Total annual expenditures in the public and private sectors to control water 

pollution are tens of billions of dollars and climbing. Monitoring is necessary to 

judge the effectiveness of these investments.

• In the last decade, it has become clear that monitoring activities need to be 

improved and integrated better to meet the full range of needs more effectively and 

economically.

Input - Output = Storage Change

Transport + Evaporation - Precipitation - Runoff – P 

=

DLand Storage+ DWater Vapor
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• A new monitoring approach is required to target water-pollution-control resources 

to priority concerns and to evaluate the effectiveness of actions taken to prevent or 

remediate problems. A better balance of ambient and compliance monitoring is 

needed.

A 2002 Report to Congress, “Concepts for National Assessment of Water Availability and Use” 

(USGS Circular 1223) (http://water.usgs.gov/pubs/circ/circ1223/) also contains some useful 

conclusions and recommendations pertaining to water monitoring:

“The assessment would develop and report on indicators of the status and trends in storage 

volumes, flow rates, and uses of water nationwide. Currently, this information is not available in 

an up-to-date, nationally comprehensive and integrated form. The development and reporting of 

national indicators of water availability and use would be analogous to the task of other Federal 

statistical programs that produce and regularly update indicator variables that describe economic, 

demographic, and health conditions of the Nation. The effort to develop indicators should comply 

with the Office of Management and Budget Information Quality Guidelines. The assessment also 

would provide regional information on recharge, evapotranspiration, interbasin transfers, and other 

components of the water cycle across the country. This regional information would support 

analyses of water availability that are undertaken by many agencies nationwide and would benefit 

research quantifying variability and changes in the national and global water cycle...”

“The assessment should be highly collaborative, involving many Federal and State agencies, 

universities, and non-governmental interests...To maximize the utility of the information, the 

design and development of the assessment should be coordinated through the Federal Advisory 

Committee on Water Information.”

6. Interagency and International Partnerships

Federal Interagency: 

• Committee on Environment and Natural Resources, Subcommittee on Water 

Availability and Quality

• Interagency Working Group on Earth Observations

• Advisory Committee on Water Information

• National Water Quality Monitoring Council

• Water Information Sharing and Analysis Center (Water ISAC)

• Window to My Environment (EPA and USGS) 

• Many bi-lateral and multi-lateral interagency collaborations

Federal-State-Tribal-Local:

• Cooperative programs with Federal agencies
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• Interstate Council on Water Policy

• Regional water councils

• River basin commissions

• Conservation Districts

Government/NGO/Academia/Private sector:

• National Drought Mitigation Center

• Stakeholder and advisory groups

• Watershed organizations

7. U.S. Capacity Building Needs

The gaps and challenges identified above could be addressed by development of consistent, 

nationwide databases for hydrologic data. This data would form the basis for reliable assessments 

and predictions of current and future conditions under various scenarios, as well as enhance our 

understanding of fundamental hydrologic processes. On a global scale, these needs are especially 

pronounced in the developing world.

8. Conclusions

The gaps and challenges identified in Table 2 and the text above indicate much work to be done in 

this area. These efforts could be coordinated through the CENR Subcommittee on Water 

Availability and Quality. There are promising indications that some hydrologic parameters such 

as soil moisture, transpiration, sediment flux, and some others may be monitored from space using 

satellites. There is also increasing use of interferometric synthetic aperture radar remote sensing 

to monitor changes in the ground surface due to changes in ground-water storage in underlying 

aquifers. Future enhancements of remote-sensing platforms may identify other hydrologic 

parameters that can be adequately monitored from space, especially where ground-based 

monitoring systems are lacking. Monitoring systems based on remote sensing will require 

adequate ground-truth data collected by in situ methods. Monitoring systems based on in situ 

methods should be maintained and expanded, and should be developed for parameters with 

currently inadequate coverage.

As mentioned above, the National Hydrography Dataset (NHD) serves as an integrating 

commonality for all data related to the surface-water flow system. It could be central to designing 

a water-data integration and retrieval system that could track water as it moves throughout the 

natural and human water cycle, including ground water. Additional work needs to be done on the 

NHD, such as completion of high-resolution hydrographic mapping on a nationwide basis, 

verification of flow relationships, and ensuring that point data are associated with individual 

stream reaches. Beyond the reach network itself, there must be strong connections with watershed 

boundary datasets. A project is underway to derive crude watershed boundaries from NHD using 

Thiessen polygons, but a more accurate approach would involve linking NHD with digital 
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elevation models (DEM’s) and using a process such as “burning and ridging” to define 

topographically accurate watershed boundaries. With these linked geospatial systems in place, 

and the appropriate connections with other data described above, we could design a data 

integration and retrieval system that would let the user point to a location on a stream, 

automatically derive a watershed boundary for that point, and then retrieve integrated point and 

area hydrologic data, from both ground-based and remote-sensing systems, sufficient to describe 

the hydrologic characteristics of that watershed and follow the flow of water through it.
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References

CENR (Committee on Natural Resources and Environment) 1997. Integrating the Nation’s

Environmental Monitoring and Research Networks and Programs, A proposed Framework. 

National Science and Technology Council, White House, Washington D.C., 100 p.

Heinz Center 2002. The State of the Nation’s Ecosystems: Measuring the Lands, Waters, and 

Living Resources of the U.S. H. John Heinz III Center for Science, Economics and the 

Environment, Washington, D.C.

Heinz Center 2003. The Coastal Zone Management Act: Developing a Framework for Identifying 

Performance Indicators. H. John Heinz III Center for Science, Economics and the Environment, 

Washington, D.C.

NRC (National Research Council) 2000. Ecological Indicators for the Nation. National Academia 

Press, Washington, D.C., 180 p.

NRC (National Research Council) 2001a. Assessing the TMDL Approach to Water Quality 

Management. National Academia Press, Washington, D.C., 109 p.

NRC (National Research Council) 2001b. Grand Challenges in Environmental Science. National 

Academia Press, Washington, D.C., 96 p.

NRC (National Research Council) 2001c. Transforming Remote Sensing Data into Information 

and Applications. National Academia Press, Washington, D.C., 75 p.

NRC (National Research Council) 2002a. Down to Earth: Geographic Information for Sustainable 

Development in Africa. National Academia Press, Washington, D.C., 155 p.

NRC (National Research Council) 2002b. Estimating Water Use in the United States. National 

Academia Press, Washington, D.C., 176 p.

NRC (National Research Council) 2002c. Opportunities to Improve the U.S. Geological Survey 

National Water Quality Assessment Program. National Academia Press, Washington, D.C., 238 p.

NRC (National Research Council) 2002d. Satellite Observations of the Earth’s Environment: 

Accelerating the Transition from Research to Operations. National Academia Press, Washington, 

D.C., 163 p.

NRC (National Research Council) 2003a. Government Data Centers. National Academia Press, 

Washington, D.C., 56 p.

NRC (National Research Council) 2003b. IT Roadmap to a Geospatial Future. National 

Academia Press, Washington, D.C., 120 p.
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NRC (National Research Council) 2003c. Satellite Observations of the Earth’s Environment. 

National Academia Press, Washington, D.C., 163 p.

USEPA 2003a. Draft Report on the Environment 2003. Office of Environmental Information and 

Office of Research and Development. U.S. Environmental Protection Agency, EPA-260-R-02-

006, Washington, D.C.

USEPA 2003b. Draft Report on the Environment 2003, Technical Document. Office of 

Environmental Information and Office of Research and Development. U.S. Environmental 

Protection Agency, EPA-600-R-03-050, Washington, D.C.

USEPA 2003c. 2003-2008 Strategic Plan. U.S. Environmental Protection Agency, Washington, 

D.C.
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APPENDIX 1

Sidebars on Uses of Hydrological Data

GEWEX Americas Prediction Project

The GAPP program (GEWEX [Global Energy and Water Cycle Experiment] America Prediction 

Project) objectives are to make monthly to seasonal predictions of the hydrological cycle and to 

use these improved predictions for better water resources management.

The first objective largely involves improving the land surface, hydrology, and boundary layer 

representations of models used for climate prediction through improved understanding of the 

hydrological processes, feedbacks between the land and atmosphere, model transferability, and 

development of a comprehensive modeling system.

The second objective involves scaling the climate model output to make it useful for water 

resource managers, improved understanding of the links between hydrologic predictions and water 

resources management, including the use of demonstration projects, and better understanding of 

the effects of land surface changes on the regional hydrology. Two major new initiatives will be 

the effect of orography on the hydrological cycle of the Western Cordillera and the predictability 

of the North American Monsoon (NAMS) and its effects on summer precipitation over the USA.

The other components all relate to improving the predictability of the hydrological cycle with 

special regards to the land surface and the role of predictions for water resources management.

Uses of Streamflow Data

Information on the flow of rivers is a vital national asset that safeguards lives and property and 

ensures adequate water resources for a healthy economy. The U.S. Geological Survey (USGS) 

operates about 7,000 streamflow-gaging stations that keep watch on the Nation’s rivers. The vast 

majority of these stations are jointly funded in partnerships with more than 800 State, local, tribal, 

and other Federal agencies. The USGS network provides real-time and long-term historical 

streamflow information that is accurate and unbiased, and that meets the needs of many users. For 

example, streamflow information is needed for:

• Flood forecasting and flood-prone area mapping,

• Planning and managing water supplies and upholding interstate compacts,

• Developing water-quality standards and monitoring changes in flow,

• Designing structures such as dams, levees, bridges, and highways.

• Avoiding unsafe or unpleasant river conditions when recreational water users plan 

their trips for fishing, canoeing, kayaking, or rafting. 

• Monitoring long-term changes in the climate.
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“Streamflow data...form the cornerstone for national, regional, and local efforts...by providing 

continued, up-to-date information about water conditions and understanding of hydrologic 

phenomena.” –National Research Council.

“The information your web page provides was very useful to our Emergency Preparedness team.” 

--Steve Durst, Sumner County Emergency Preparedness, Welling, Kansas.

“The federal cost of basic water data collection and analysis pales when compared to the cost of 

facilities which will be based on inadequate data, as well as to the potential loss of life and 

property that can occur if errors in design result from use of a faulty data base.” –American 

Society of Civil Engineers.

Water 2025

Water 2025 (http://www.doi.gov/water2025/) is a new problem-solving initiative by the U.S. 

Department of the Interior that will help manage scarce water resources in the western U.S., and 

develop partnerships to nourish a healthy environment and sustain a vibrant economy. In some 

areas of the West, existing water supplies are, or will be, inadequate to meet the demands for water 

for people, cities, farms, and the environment even under normal water supply conditions. For 

Fiscal Year 2025, 19 projects have been identified in 10 western states to enhance understanding 

and management of scarce water resources so that conflicts will be avoided or minimized. 

Projects will focus on water marketing, conservation, augmentation, and management. 

Underlying these projects will be a continuing need for reliable, impartial data about the water 

resources subject to conflict.