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Final Report: Vulnerability of Water Resources to Global Climate Change in the Agricultural Midwest Ecological, Economic and Regulatory Aspects

EPA Grant Number: R824804
Title: Vulnerability of Water Resources to Global Climate Change in the Agricultural Midwest Ecological, Economic and Regulatory Aspects
Investigators: Eheart, J. Wayland , Herricks, Edwin E.
Institution: University of Illinois at Urbana-Champaign
EPA Project Officer: Winner, Darrell
Project Period: October 1, 1995 through September 1, 1998 (Extended to September 30, 1998)
Project Amount: $380,000
RFA: Regional Hydrologic Vulnerability to Global Climate Change (1995)
Research Category: Global Climate Change , Ecological Indicators/Assessment/Restoration

Description:

Objective:

The purpose of this project was to estimate the direct and indirect effects of climate change on water resources in the Midwest. Direct effects include those changes such as reduced altered streamflows caused by more variable rainfall. Indirect effects include the effects of such changes on water quality, fish and fish communities or how natural change can be exacerbated by an increase in the level of adoption of irrigation by Midwestern farmers in response to increasing climate dryness.

Summary/Accomplishments (Outputs/Outcomes):

In this work, we address two basic questions: (1) what are the consequences of climate change-related hydrologic variability, and (2) what we can do about it. The project was divided into four basic activities, described as follows. Three of the activities fall in the first category of estimating how consequential the climate change effects could become; the fourth falls in the second category of exploring means of solving the problem.

Altered Low Flow Frequency. One of the issues we addressed was to describe how streamflows might be altered by expected climate change. We estimated how the frequency and duration of a widely-accepted low flow event, the historical seven-day-ten-year low flow (7Q10), might be affected by: (1) a drier climate, (2) a more variable one, or (3) one that has both characteristics. In doing so, we examined both direct and indirect effects as discussed above. The results are summarized in Figure 1, which shows the frequency of low flow occurrences for several different weather change scenarios and sets of assumptions about farming practices.

Figure 1

This graph presents the results of simulations of the distribution of the number of days per year that the streamflow in the Sangamon River at Monticello, Illinois falls below its historical (pre-climate change) value under a reduction in mean precipitation of 25 percent relative to the historical mean at the National Weather Service station at Farmer City, Illinois. The lines on the graph represent different assumptions about irrigation practice. The solid lines represent irrigation in a manner that maximizes farm yields; the dashed lines except for the one labeled "No Irrigation" represent a profit maximizing strategy, and that latter line represents no irrigation in the basin at all. It was assumed that upstream of the Monticello gauge, a 13,000 ha strip on each side of the river is capable of being irrigated by river-supplied irrigation, and that the indicated percentage of that land is in fact supplied by the river. The remainder of the strip, as well as the rest of the basin, is assumed supplied by groundwater.

The principal message of this graph is that if climate change induces widespread surface supplied irrigation it can threaten streams. The graph shows that yield maximizing behavior is worse than profit maximizing behavior, but that both could have substantial effect on the frequency of low streamflow events. Consistent behavior was shown by the results for other climate scenarios, which consisted of three other precipitation scenarios. These are: (1) historical mean and standard deviation, (2) historical mean but twice the historical standard deviation, and (3) 25 percent reduction in mean and twice the historical standard deviation. Results of this work, model calibration, and further information on the material discussed above are presented by Eheart and Tornil, 1999.

Change In Criterion Low Flow. Other questions relate to the effect of climate change on water quality. In the process that sets water quality standards, a design flow is accepted as a minimum dilution flow for calculating point source discharge permit limits. This design flow is critical because of the high likelihood that water quality standards will be violated below these design flows. We estimated the change in magnitude of the one-day and seven-day-ten-year low flows (1Q10) and (7Q10) flows using climate and irrigation scenarios used to assess flow frequency changes. The (1Q10) and (7Q10) flows are important because these flows are used for water quality planning and constitute the design flows used in current water quality management programs such as total maximum daily load (TMDL) determinaitons. We determined the (1Q10) and (7Q10) from those data by standard techniques.

Table 1 summarizes the results under 20 scenarios for the example basin, the Sangamon River above Monticello, Illinois. For each scenario, the 1Q10 and 7Q10 flows, and their departure (percent change) from an equivalent base case scenario (defined below), are reported. It should be noted that, because this analysis is based on 100 years of synthetic data, the 1Q10 and 7Q10 flows, even for the case with no irrigation and no climate change, are not the same as the historical 1Q10 and 7Q10 flows. For the scenarios that incorporate irrigation and no climate change, the equivalent base case scenario is taken as the scenario called "0%" (i.e., neither irrigation nor climate change). For scenarios representing both irrigation and climate change, the equivalent base case scenario is that with the same irrigation assumptions but no climate change. In cases where the low flow for the scenario drops to zero, but the equivalent base case scenario is above zero, the change is listed as -100 percent. In cases where both the altered scenario and the equivalent base case scenario have a low flow of zero, the entry is "NA."

The scenario code summarizes the precipitation change, the irrigation strategy, and the limitations on water withdrawal. The code is written XYZ, where X represents one of four climate change scenarios: (1) no change in precipitation (0%); (2) decreasing the mean precipitation by 25% (-25%); (3) doubling the standard deviation of precipitation (2SD); and (4) decreasing the mean precipitation by 25% and doubling the standard deviation (-25%&2SD). Y represents one of three irrigation strategies: no irrigation (if blank), the profit maximizing (PM) trigger of 125 or 150 mm, or the yield maximizing (YM) trigger of 15 mm. Z is set to either 0 or 7, indicating either the zero or 7Q10 streamflow limitation on water withdrawal, respectively. Z is blank for scenarios where no irrigation occurs.

Scenario 1Q10 % change 7Q10 % change
0% 0.067 m3/s NA 0.077 m3/s NA
0%PM7 0.054 m3/s -20% 0.078 m3/s +2%
0%YM7 0.054 m3/s -20% 0.054 m3/s -30%
0%PM0 0.0 m3/s -100% 0.078 m3/s +2%
0%YM0 0.0 m3/s -100% 0.0 m3/s -100%
-25% 0.024 m3/s -64% 0.028 m3/s -63%
-25%PM7 0.025 m3/s -55% 0.029 m3/s -64%
-25%YM7 0.030 m3/s -44% 0.0347 m3/s -36%
-25%PM0 0.0 m3/s NA 0.0350 m3/s -55%
-25%YM0 0.0 m3/s NA 0.0 m3/s NA
2SD 0.029 m3/s -57% 0.033 m3/s -57%
2SDPM7 0.029 m3/s -54% 0.033 m3/s -57%
2SDYM7 0.030 m3/s -44% 0.035 m3/s -36%
2SDPM0 0.0 m3/s NA 0.033 m3/s -57%
2SDYM0 0.0 m3/s NA 0.0 m3/s NA
-25%&2SD 0.0106 m3/s -84% 0.012 m3/s -84%
-25%&2SDPM7 0.0108 m3/s -80% 0.013 m3/s -84%
-25%&2SDYM7 0.013 m3/s -76% 0.015 m3/s -73%
-25%&2SDPM0 0.0 m3/s NA 0.012 m3/s -84%
-25%&2SDYM0 0.0 m3/s NA 0.0 m3/s NA

Table 1. 1Q10 and 7Q10 Flows for Different Scenarios

This table demonstrates that either climate change or irrigation may have a severe effect on low flow regimes, whether or not the other is considered. The scenarios with climate change and no irrigation (-25%, 2 SD, and -25% & 2 SD) show a reduction of from 57 to 84 percent. The scenarios with irrigation and no climate change, 0% PM7 through 0% YM0 in Table 2, show changes ranging from a slight increase to a 30% decrease (ignoring the degenerate cases with a critical design flow of zero). The scenarios that combine irrigation and climate change show critical design flow changes in the same range. Thus, under these global climate change scenarios, the stream would only be allowed to assimilate as little as 16 percent of the wasteload as under a design using historical low flow values. Moreover, under the current system, which does not limit the amount farmers may withdraw from surface water, the 1Q10 flows for this portion of the river are expected to go to zero. Further results of this part of the research, which is omitted here for brevity, is devoted to determining how many days per year the flow falls below the historical low flows and how many events of multiple years of violation of those low flow criteria occur. These results are described more fully by Eheart, Wildermuth, and Herricks (1999).

Vulnerability of Natural Resources?Effect of Climate Change on Fisheries. A third set of questions related to the vulnerability of natural resources to climate change. With a change in stream flow, we can expect that habitat conditions in streams and rivers will also change. We examined the the effects of flow variability on the expected habitat available for a twenty-four common Midwestern fish species (Black Crappie, Bluegill, Bluntnose Minnow, Creek Chub, Channel Catfish, Carp, Freshwater Drum, Fantail Darter, Gizzard Shad, Greenside Darter, Green Sunfish, Longear Sunfish, Largemouth Bass, Log Perch, Northern Pike, Rock Bass, Rainbow Darter, Smallmouth Bass, Striped Shiner, Stonecat, White Bass, White Crappie, Walleye, and White Sucker). In this analysis the PHysical HABitat SIMulation (PHABSIM) model was used to assess how habitat might change with changing flow conditions for both adults and eaarlier life stages. An initial analysis that compared habitat estimates under various climate change-related flow scenarios revealed change. Point-in-time estimates of habitat availability did not provide the necessary time-sequenced information to confirm subtle effects of climate change on fish communities. To address this shortcoming, the PHABSIM habitat estimates were also used to model fish populations in target reaches. Models were constructed for six species (Channel Catfish, Greenside Darter, Green Sunfish, Longear Sunfish, Largemouth Bass and Smallmouth Bass). These models used PHABSIM generated habitat as a limiting factor in population predictions. A typical model structure is provided in Figure 2. Models were calibrated based on historical fishereis collection data from the Sangamon River dating to the late 1800s.

Figure 2

The fish population modeling identified important effects of climate change on fish populations, and likely fisheries community composition. Species life history was identified as an important factor in both effect severity and the capacity of organisms to recover from events with significant population consequence. Duration time of the event was more critical for species with short life histories where a two year sequence of altered flow reduced populations. Species with longer life histories withstood short duration alterations better. This modeling approach provides new insight into the effects of more variable climate/runoff scenarios, by allowing analysis of both adult and early life stage response to changing habitat.

Water Withdrawal Permitting and Trading. The final project activity is directed toward the second overall question, viz., what can be done to address the direct and indirect effects of climate change. We considered regulations to limit water withdrawals, but included as an option a measure of flexibility in those regulations in the form of transferable withdrawal permits. In essence, permit transferability is important in maintaining both critical streamflows and farm profitability because it enables water rights to be sufficiently consolidated to justify the capital expense of irrigation equipment. It follows that, with fewer users taking water from the stream, the withdrawal rates on critical days and adjacent days are less than in the absence of trading. This is shown by Figure 2, which shows the low-flow frequency under several combinations of scenarios for climate, agricultural practice, and trading of withdrawal permits. The lines labeled "25% area" represent the consolidation of permits to 25 percent of the surface-irrigable land, which is estimated as optimal by the models. It is assumed that this consolidation would occur by trading in a market in which riparian landowners would be paid by other riparian landowners to give up their rights to water. Lines labeled "50%" represent regulation of water withdrawal, whether trading is allowed or not, under which no more than 50 percent of the streamflow is allocated to irrigation. The other variable is climate change which is represented by either a 25 percent precipitation decrease or no climate change ("No CC").

Other work in this part of the project was directed at investigating different forms of water withdrawal regulation (e.g., fixed daily allowances and percentages of streamflow other than 50 percent) and determining farm profits under all these scenarios. It was found that total basin profits are only slightly less under a 50 percent percent flow regulation with trading than when withdrawals are completely unregulated. Note that the above graph shows a substantial worsening in low flow frequency when withdrawals are unregulated. These results are described more fully by Wollmuth and Eheart (1999).


Journal Articles on this Report: 3 Displayed | Download in RIS Format

Other project views: All 14 publications 3 publications in selected types All 3 journal articles

Type Citation Project Document Sources
Journal Article Eheart JW, Wildermuth AJ, Herricks EE. The effects of climate change and irrigation on criterion low streamflows used for determining total maximum daily loads. Journal of the American Water Resources Association 1999;35(6):1365-1372. R824804 (Final)
 not available
Journal Article Eheart JW, Tornil DW. Low-flow frequency exacerbation by irrigation withdrawals in the agricultural midwest under various climate change scenarios. Water Resources Research 1999;35(7):2237-2246 R824804 (Final)
 not available
Journal Article Wollmuth JJC, Eheart JW. Surface water withdrawal allocation and trading systems for traditionally riparian areas. Journal of the American Water Resources Association 2000;36(2):293-303. R824804 (Final)
 not available
Supplemental Keywords:

midwest, climate change, SWAT, hydrology, irrigation, low flow, droughts, water, watershed, global climate, vulnerability, socioeconomic, climate models, Region 5. , Ecosystem Protection/Environmental Exposure & Risk, Water, Air, Geographic Area, Scientific Discipline, RFA, Ecosystem/Assessment/Indicators, Water & Watershed, exploratory research environmental biology, climate change, Ecological Risk Assessment, Ecological Indicators, Ecological Effects - Human Health, EPA Region, Hydrology, Watersheds, Chemical Mixtures - Environmental Exposure & Risk, Ecological Effects - Environmental Exposure & Risk, Ecosystem Protection, precipitation patterns, risk assessment, toxic environmental contaminants, alternative urbanization scenarios, drinking water supplies, Global Climate Change, hydrologic models, precipitation, socioeconomic indicators, watershed, crop production, farming, habitat diversity, climatic models, fish habitat, land use, policy making, farm income, toxics, economic models, environmental monitoring, Region 5, climate models, agricultural watershed, availability of water resources, climate variability, land and water resources, Midwestern agriculture, urban growth, water resources, streamflow sensitivity

Progress and Final Reports:
1998 Progress Report
Original Abstract

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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