Water Withdrawals in Water Stressed Areas: Impacts of the Steam Electric Effluent 

Limitations Guidelines

Patrick Walsh and Matt Massey, OP/NCEE

Introduction

Steam electric power plants use large quantities of water. Power plants using a thermal cycle 

employing steam to generate electricity, which will be regulated in the new effluent limitations 

and guidelines (ELGs), use water in several parts of the thermodynamic process that drives the 

steam engine. Additionally, steam electric plants use vast amounts of water for cooling, ash 

handling, and the operation of wet flue gas desulfurization (FGD) scrubbers. The United States 

Geological Survey (USGS) estimated on a national level that 41% of all freshwater withdrawals 

in the United States in 2005 were for thermoelectric power operations, primarily for cooling 

needs (USGS, 2009).

1 Given the importance of water to this power sector, it is therefore highly 

vulnerable to changes in the availability and condition of water (USDE 2013). Droughts and 

severe dry conditions can lead to diminished electricity production and water-related shutdowns, 

due to shallow or exposed cooling water intake locations and water temperatures too high for 

proper cooling, among other reasons (NETL, 2009; Eaton, 2012). Since current forecasts indicate 

that climate change will result in more frequent and severe droughts (Feely et al., 2008), the 

impacts on the power sector may expand in the future.

A number of steam electric power plants operate in regions of the country that experience regular 

or intermittent drought conditions. Several of the proposed regulatory options have requirements 

that would reduce the amount of intake water required at each plant. For example, by eliminating 

or reducing water used in ash sluicing operations, the proposed ELGs are expected to reduce 

water withdrawal from both surface waterbodies and aquifers. To investigate the impacts of the 

rule on facilities in water stressed areas, this section explores the exposure of the regulated 

community to drought-related conditions and quantifies the reduced water intake in waterstressed areas.

Background

Due to the dependence of steam electric power plants on intake water, increased water scarcity 

and temperature can induce a range of negative impacts, including higher electricity prices, 

shutdowns, diminished production, and higher emissions.2 Several recent drought-prone 

summers have exposed a number of these negative impacts. Summers present a particularly 

troubling time for this industry, as drought conditions worsen and air conditioning usage

increases power demand. 

 1 In 2005, 71% of thermoelectric water withdrawals were from freshwater sources (Kenny et al 2009). Saline withdrawals are 

primarily concentrated in California, Florida and the coastal northeast, with the rest of the country relying on freshwater. 2 Eyer and Wichman (2014) explore emissions impacts of droughts on the power sector.
For example, the severe drought experienced in Texas in 2011 resulted in low water reservoir 

levels at a number of Texas power plants. A number of plants were forced to either reduce their 

generation or pump in the needed water from distant locations (Scanlon et al. 2013). The 2007 

drought in the southeast forced nuclear and coal-fired plants within the TVA system to shut 

down some reactors and curtail operations in others (DOE/NETL 2009). Record heat and 

drought in 2012 caused shutdowns as far north as Connecticut, when the Long Island Sound 

reached temperatures too high to be used as cooling water (Eaton, 2012). 

Water availability can also have several other indirect effects. McDermott and Nilsen (2014) 

found that high water temperatures and reduced availability both contribute to higher electricity 

prices. Eyer and Wichman (2014) examine several implications of water supply shocks and find 

that hydroelectric generation is reduced in favor of coal and natural gas. They also find that 

pollutant emissions increase as a result of water scarcity. Another important externality of water 

withdrawals is the impingement and entrainment of aquatic organisms. Although quantifying the 

effect is beyond the scope of this analysis, the regulatory options of the present rule that reduce 

water withdrawals will also likely reduce these impacts to aquatic life (US EPA, 2014).

Analysis

The technology options for fly ash and bottom ash proposed in the Steam Electric ELGs will 

eliminate or reduce water use associated with current wet sluicing operating systems. EPA 

estimated the reductions in water use by calculating the amount of ash transport water, 

specifically that amount of water identified as intake process water that will no longer be 

discharged as part of the proposed rulemaking. In order to calculate this reduction, EPA used 

data from Part C of the Steam Electric Survey to calculate an average percentage of ash transport

water identified as intake water. EPA multiplied this percentage by the amount of transport water 

discharged by each plant to calculate the estimated process water reduction. See the 

memorandum entitled “Steam Electric Effluent Guidelines Non-Water Quality Impacts” for 

more information (ERG, 2013). To minimize double counting between rules, for all units that are 

projected to be converting to dry ash handling of fly ash or bottom ash under the CCR Rule, a 

0% reduction was assumed. So if a unit is converting under the CCR Rule, there are no 

additional reductions for the Final ELG rule. 

In calculating the impact on intake water, we present two estimates for each plant. The first

estimate (referred to in Tables 2 and 3 as Maximum Recycle), assumes units that currently 

recycle at least a portion of transport water will have a reduction in intake flow that is equal to 

the discharge flow. That would be accomplished by eliminating the intake water requirements

using recycled transport water (i.e., 100% of discharge flow is the reduction in intake flow). The 

second, referred to as the intake reduction only, is based on the percentage of the ash transport 

flow that comes from intake water indicated by the plant in their survey response and represents 

a more conservative estimate. These two estimates therefore represent a possible range of water 

use reductions under the rule.
To examine the exposure of regulated steam electric plants to drought, we use drought maps 

from the US Drought Monitor, which are produced jointly by the National Oceanic and 

Atmospheric Administration (NOAA), the US Department of Agriculture (USDA), and the 

National Drought Mitigation Center (NDMC) at the University of Nebraska Lincoln.3 The US 

Drought Monitor releases weekly maps of drought conditions, indicating the spatial extent of 

water stressed areas. Figure 1 shows an example of these maps, one from the week of May 19th, 

2009, and the other from the week of July 1st, 2014. This analysis uses categories D0-D4 from 

drought monitor to classify water-stressed areas.4

Figure 1: Example Drought Maps from US Drought Monitor

Findings

Using GIS, plant locations from the Steam Electric survey were overlaid on weekly drought 

maps for the years 2009 through 2014. To present a broad view of facilities in water-stressed 

areas, Table 1 portrays the distribution of all plants that would be affected by the technology 

requirements for fly ash and bottom ash under regulatory option D. Plants are sorted by the 

number of weeks they were in water stressed conditions. For example, in 2009, 41 plants had

between 1-5 water stressed weeks, while 31 plants experienced 6 to 10 water stressed weeks.

 3 The maps are hosted by NDMC at http://droughtmonitor.unl.edu/Home.aspx 4 The lowest of these categories is “abnormally dry,” which usually precedes or follows a drought, and is 

characterized by damage to crops and water deficits. These water deficits and other associated conditions could 

impact the operation of steam electric plants. See 

http://droughtmonitor.unl.edu/AboutUs/ClassificationScheme.aspx for additional information.
Under the preferred options of the proposed ELGs many of these will experience decreased 

water withdrawals.

Table 1. Number of Steam Electric Power Plants and Weeks (May-October) in Water 

Stressed Conditions

# of Weeks 2009 2010 2011 2012 2013 2014

0 108 60 50 2 68 96

1-5 41 42 36 11 42 53

6-10 31 49 41 20 26 20

11-15 11 34 29 32 30 13

16-20 5 17 17 39 13 7

21-25 4 2 9 72 29 19

26 8 4 27 32 0 0

Total 208 208 208 208 208 208

At Least One Week 100 148 154 206 146 112

Table 2 narrows the focus to plants that will reduce their water intake under Option D of the 

Final Steam Electric ELG (which would establish requirements that lead to dry handling of fly 

ash and dry handling or closed-loop operation for bottom ash) that faced at least one week of 

drought-like conditions, by year (between May and October) from 2009 to 2014. The first 

column of the table presents the number of those plants located in one of the water stressed areas 

contained in the Drought Monitor maps. The table indicates 2012 was a particularly dry year, 

with 98 plants operating under at least one week of drought-related conditions. The later columns 

of Table 2 calculate the reductions in water withdrawals in millions of gallons per day (MGD)

that would have been achieved under regulatory Option D by those plants.5 Between 2009 and 

2014, the average amount of intake water reduced would have been 138 – 146 million gallons

per day. This translates to an annual average of 50-53 billion gallons of water no longer 

withdrawn from drought-prone areas.

Table 2. Plants that would Reduce Water Intake under Option D with at Least 1 Week of 

Water-Stressed Conditions

Year (May-Oct.) # of Plants

Reduced Water Intake, 

Intake Reduction Only 

(MGD) 

Reduced Water Intake,

Maximum Recycle 

Reduction (MGD)

2009 41 59.8 63.8

2010 63 170.6 178.5

2011 76 172.8 184.8

2012 98 209.5 222.7

 5 Note that the MGD figures should not be added across columns, because there will be overlap in facilities affected 

across years.
2013 70 133.8 142.9

2014 47 81.8 85.2

Average MGD --- 138.1 146.3

Annual Average 

(Average MGD*365)

--- 50,393.1 53,402.2

Finally, examining areas with more chronic drought-like conditions, Table 3 presents the

potential intake water reductions from Option D for plants with at least 5 or 10 weeks of water 

stressed conditions. Across the years 2009-2014, the average reductions in water intake for 

plants under at least 5 weeks of water-stressed conditions is projected to be 105 – 112 MGD. 

This translates to 38-41 billion gallons across an entire year. For facilities under at least 10 

weeks of water stressed conditions, the average water reduced is projected to be 75-80 MGD, 

which corresponds to approximately 27 -29 billion gallons reduced per year.

Table 3. Water Intake Reductions under Option D for Plants under Water Stressed 

Conditions for at least 5 or 10 Weeks.

At Least 5 

Weeks

At Least 5 

Weeks

At Least 10 

Weeks

At Least 10 

Weeks

Intake Only 

Reduction

(MGD)

Maximum 

Recycle 

Reduction

(MGD)

Intake Only 

Reduction

(MGD)

Maximum 

Recycle 

Reduction

(MGD)

2009 38.0 40.1 15.8 17.4

2010 90.3 96.3 72.8 78.4

2011 155.1 166.4 77.1 79.8

2012 195.7 208.9 192.8 205.5

2013 111.7 119.9 74.3 82.2

2014 38.0 40.5 14.1 14.7

Average 2009-2014 104.8 112.0 74.5 79.7

Annual Gallons 

(Average 2009-

2014 MGD*365)

38,256.5 40,887.8 27,189.4 29,078.9

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