INFLUENCES OF WATERSHED URBANIZATION AND INSTREAM HABITAT ON MACROINVERTEBRATES IN COLD WATER STREAMS1

ABSTRACT: We analyzed data from riffle and snag habitats for 39 small cold water streams with different levels of watershed urbanization in Wisconsin and Minnesota to evaluate the influences of urban land use and instream habitat on macroinvertebrate communities. Multivariate analysis indicated that stream temperature and amount of urban land use in the watersheds were the most influential factors determining macroinvertebrate assemblages. The amount of watershed urbanization was nonlinearly and negatively correlated with percentages of Ephemeroptera‐Plecoptera‐Trichoptera (EPT) abundance, EPT taxa, filterers, and scrapers and positively correlated with Hilsenhoff biotic index. High quality macroinvertebrate index values were possible if effective imperviousness was less than 7 percent of the watershed area. Beyond this level of imperviousness, index values tended to be consistently poor. Land uses in the riparian area were equal or more influential relative to land use elsewhere in the watershed, although riparian area consisted of only a small portion of the entire watershed area. Our study implies that it is extremely important to restrict watershed impervious land use and protect stream riparian areas for reducing human degradation on stream quality in low level urbanizing watersheds. Stream temperature may be one of the major factors through which human activities degrade cold‐water streams, and management efforts that can maintain a natural thermal regime will help preserve stream quality.     

PATTERNS OF WATERSHED URBANIZATION AND IMPACTS ON WATER QUALITY1

ABSTRACT: Urban runoff contributes to nonpoint source pollution, but there is little understanding of the way that pattern and extent of urbanization contributes to this problem. Indicators of type and density of urbanization and access to municipal services were examined in six urban watersheds in Durham, North Carolina. Principal components analysis (PCA) was used to identify patterns in the distribution of these variables across the urban landscape. While spatial variation in urban environments is not perfectly captured by any one variable, the results suggest that most of the variation can be explained using several variables related to the extent and distribution of urban development. Multiple linear regression models were fit to relate these urbanization indicators to total phosphorus, total kjeldahl nitrogen, total suspended solids, and fecal coliforms. Development density was correlated to decreased water quality in each of the models. Indicators of urbanization type such as the house age, amount of contiguous impervious surface, and stormwater connectivity explained additional variation. In the nutrient models, access to city services was also an important factor. The results indicate that while urbanization density is important in predicting water quality, indicators of urbanization type and access to city services help explain additional variation in the models.     

EFFECTS OF WATERSHED BEST MANAGEMENT PRACTICES ON HABITAT AND FISH IN WISCONSIN STREAMS1

ABSTRACT: We evaluated the effectiveness of watershed‐scale implementations of best‐management practices (BMPs) for improving habitat and fish attributes in two coldwater stream systems in Wisconsin. We sampled physical habitat, water temperature, and fish communities in multiple paired treatment and reference streams before and after upland (barnyard runoff controls, manure storage, contour plowing, reduced tillage) and riparian (stream bank fencing, sloping, limited rip‐rapping) BMP installation in the treatment subwatersheds. In Spring Creek, BMPs significantly improved overall stream habitat quality, bank stability, instream cover for fish, abundance of cool‐ and coldwater fishes, and abundance of all fishes. Improvements were most pronounced at sites with riparian BMPs. Water temperatures were consistently cold enough to support coldwater fishes such as trout (Salmonidae) and sculpins (Cottidae) even before BMP installation. We observed the first‐time occurrence of naturally reproduced brown trout (Salmo trutta) in Spring Creek, indicating that the stream condition had been improved to be able to partially sustain a trout population. In Eagle Creek and its tributary Joos Creek, limited riparian BMPs led to localized gains in overall habitat quality, bank stability, and water depth. However, because few upland BMPs were installed in the subwatershed there were no improvements in water temperature or the quality of the fish community. Temperatures remained marginal for coldwater fish throughout the study. Our results demonstrate that riparian BMPs can improve habitat conditions in Wisconsin streams, but cannot restore coldwater fish communities if there is insufficient upland BMP implementation. Our approach of studying multiple paired treatment and reference streams before and after BMP implementation proved effective in detecting the response of stream ecosystems to watershed management activities.     

WATERSHED URBANIZATION AND CHANGES IN FISH COMMUNITIES IN SOUTHEASTERN WISCONSIN STREAMS1

ABSTRACT: We compared watershed land‐use and fish community data between the 1970s and 1990s in 47 small streams in southeastern Wisconsin. Our goal was to quantify effects of increasing urbanization on stream fishes in what had been a predominantly agricultural region. In the 43 test watersheds, mean surface coverage by agricultural lands decreased from 54 percent to 43 percent and urban lands increased from 24 percent to 31 percent between 1970 and 1990. Agriculture dominated the four reference watersheds, but neither agriculture (65–59 percent) nor urban (4.4–4.8 percent) land‐uses changed significantly in those watersheds during the study period. From the 1970s to the 1990s the mean number of fish species for the test stream sites decreased 15 percent, fish density decreased 41 percent, and the index of biotic integrity (IBI) score dropped 32 percent. Fish community attributes at the four reference sites did not change significantly during the same period, although density was substantially lower in the 1990s. For both the 1970s and 1990s test sites, numbers of fish species and IBI scores were positively correlated with watershed percent agricultural land coverage and negatively correlated with watershed urban land uses, as indexed by percent effective connected imperviousness. Numbers of fish species per site and IBI scores were highly variable below 10 percent imperviousness, but consistently low above 10 percent. Sites that had less than 10 percent imperviousness and fewer than 10 fish species in the 1970s suffered the greatest relative increase in imperviousness and decline in species number over the study period. Our findings are consistent with previous studies that have found strong negative effects of urban land uses on stream ecosystems and a threshold of environmental damage at about 10 percent imperviousness. We conclude that although agricultural land uses often degrade stream fish communities, agricultural land impacts are generally less severe than those from urbanization on a per‐unit‐area basis.     

QUANTIFICATION OF INSTREAM FLOW NEEDS OF A WILD AND SCENIC RIVER FOR WATER RIGHTS LITIGATION1

ABSTRACT: The lower 4 miles of the Red River, a tributary of the Rio Grande in northern New Mexico, was designated as one of the “instant” components of the National Wild and Scenic River System in 1968. The Bureau of Land Management (BLM), as the managing agency of the wild and scenic river, was a participant in a general water rights adjudication of the Red River stream system. The BLM sought a federal reserved water right and asserted a claim to the instream flows necessary to protect and maintain the values of the river. Instream flows are not recognized under New Mexico water law. Instream flow requirements were determined by several methods to quantify the claims made by the United States for a federal reserved water right under the Wild and Scenic Rivers Act. The scenic (aesthetic), recreational, and fish and wildlife values are the purposes for which instream flow requirements were claimed. Since water quality is related to these values, instream flows for waste transport and protection of water quality were also included in the claim. The U.S. Fish and Wildlife Service's Instream Flow Incremental Methodology was used to quantify the relationship between various flow regimes and fish habitat. Experience in this litigation indicates the importance of using state-of-the-art methodologies in quantifying instream flow claims. The incremental methodology held up well under technical and legal scrutiny and is an example of the latest methodology that was applied successfully in an adjudication. On February 23, 1984, the parties involved in the adjudication entered a precedential stipulation recognizing a federal reserved right to instream flows for the Red River component of the National Wild and Scenic River System.     

COOPERATIVE MANAGEMENT OF THE DUNGENESS WATERSHED TO PROTECT SALMON IN WASHINGTON STATE1

ABSTRACT: Over the last decade, the Jamestown S'Klallam Tribe has formed partnerships with their neighboring county government, irrigation districts, property owners, and state and federal agencies in an effort to save the dwindling runs of Dungeness River salmon. Although considerable progress has been made to begin the recovery process, the watershed is included in recent listings of Pacific Northwest salmon under the Endangered Species Act. Under the coordination of an active watershed council, significant improvements have been made in water conservation and the protection of instream flows. Cooperation between the Tribe, irrigation districts and the Washington Department of Ecology resulted in a trust water rights agreement and the reduction of late summer water withdrawals by one‐third.     

HYDROLOGICAL MODELING OF THE IROQUOIS RIVER WATERSHED USING HSPF AND SWAT1

ABSTRACT: The performance of two popular watershed scale simulation models — HSPF and SWAT — were evaluated for simulating the hydrology of the 5,568 km² Iroquois River watershed in Illinois and Indiana. This large, tile drained agricultural watershed provides distinctly different conditions for model comparison in contrast to previous studies. Both models were calibrated for a nine‐year period (1987 through 1995) and verified using an independent 15‐year period (1972 through 1986) by comparing simulated and observed daily, monthly, and annual streamflow. The characteristics of simulated flows from both models are mostly similar to each other and to observed flows, particularly for the calibration results. SWAT predicts flows slightly better than HSPF for the verification period, with the primary advantage being better simulation of low flows. A noticeable difference in the models' hydrologic simulation relates to the estimation of potential evapotranspiration (PET). Comparatively low PET values provided as input to HSPF from the BASINS 3.0 database may be a factor in HSPF's overestimation of low flows. Another factor affecting baseflow simulation is the presence of tile drains in the watershed. HSPF parameters can be adjusted to indirectly account for the faster subsurface flow associated with tile drains, but there is no specific tile drainage component in HSPF as there is in SWAT. Continued comparative studies such as this, under a variety of hydrologic conditions and watershed scales, provide needed guidance to potential users in model selection and application.     

DISTRIBUTION AND STOCHASTIC GENERATION OF ANNUAL AND MONTHLY PRECIPITATION ON A MOUNTAINOUS WATERSHED IN SOUTHWEST IDAHO1

ABSTRACT: The 18-year precipitation record from the dense gage network on the Reynolds Creek Experimental Watershed located in southwest Idaho was used to determine the spatial distribution of annual and monthly precipitation on a mountainous watershed. Analyses of these data showed a linear relationship between annual amounts and elevation. This relationship was best when the gages were grouped into downwind and upwind sites. This grouping was appropriate because most of the winter storms moved over the watershed from the west and southwest, and the heaviest precipitation was on the west (downwind) side of the watershed. Gage sites along the western and southern watershed borders were most representative of the upwind gages on the east side, because they measured the precipitation from the air moving upwind onto the watershed. The maximum annual precipitation on the watershed was just leeward of the western watershed boundary. The monthly precipitation and elevation relationship was also best represented by grouping the gage sites into upwind and downwind sites. However, during the summer when there are only small amounts of pre cipitation and thunderstorms are the source of most precipitation, one equation can be used to represent the elevation relationship. This study also showed that the log-normal distribution could be used to generate the annual synthetic series, and the cube-root-normal distribution could be used to generate monthly synthetic series for all locations on the watershed.     

THE POTENTIAL IMPACT OF WATER REALLOCATIONS ON AGRICULTURE IN IDAHO1

ABSTRACT: Economics is concerned with the allocation of resources between alternative uses. Traditionally, in the western United States, water resources have been committed to agriculture and irrigation. Other competitive uses such as power, industry, and recreation are challenging this allocation. What are the impacts of shifting water out of agriculture into other uses, is a question that needs to be given consideration. Ilia paper attempts to evaluate the tradeoff between using farm land for either irrigated or dryland production and the resulting impacts on gross farm income and the average price of land. Baaed on historical data, reducing irrigated acreage and increasing dryland acreage could greatly reduce both farm income and the equity in farming. The model presented in this paper should be useful for evaluating the tradeoffs between dryland and irrigated land use, especially when there are gat differences in productivity such as those that exist in the inter-mountain region of the Western United States.     

LONG-TERM CHANGES IN LOW-FLOW CHANNEL WIDTHS WITHIN THE SOUTH UMPQUA WATERSHED,OREGON1

ABSTRACT: Recent stream survey data (1989–1993) from 31 stream segments of 21 streams within the upper South Umpqua Watershed Oregon were compared to 1937 stream survey data collected from these same stream segments. Current low-flow wetted stream widths of 22 of the 31 surveyed stream segments were significantly different than in 1937; 19 stream segments were significantly wider while the remaining three stream segments were significantly narrower. In only 1 of 8 tributaries to the South Umpqua River which had headwaters within land designated wilderness area did low-flow stream channel width increase since 1937. Conversely, 13 of the 14 tributaries to the South Umpqua River which originated from lands designated as timber emphasis were significantly wider than in 1937. The observed change in stream width was linearly related to timber harvest (r²= 0.44), road density (r²= 0.45), and the amount of large organic debris remaining within the active stream channel (r²= 0.43). These findings suggest that timber harvest and road construction may have resulted in changes in channel characteristics. These channel changes may also be a factor in the observed decline of three of the four populations of anadromous salmonids within the basin.     

CLIMATE CHANGE IMPACTS ON WATER RESOURCES OF THE TSENGWEN CREEK WATERSHED IN TAIWAN1

ABSTRACT: This study presents a methodology to evaluate the vulnerability of water resources in the Tsengwen creek watershed, Taiwan. Tsengwen reservoir, located in the Tsengwen creek watershed, is a multipurpose reservoir with a primary function to supply water for the ChiaNan Irrigation District. A simulation procedure was developed to evaluate the impacts of climate change on the water resources system. The simulation procedure includes a streamflow model, a weather generation model, a sequent peak algorithm, and a risk assessment process. Three climate change scenarios were constructed based on the predictions of three General Circulation Models (CCCM, GFDL, and GISS). The impacts of climate change on streamflows were simulated, and, for each climate change scenario, the agricultural water demand was adjusted based on the change of potential evapotranspiration. Simulation results indicated that the climate change may increase the annual and seasonal streamflows in the Tsengwen creek watershed. The increase in streamflows during wet periods may result in serious flooding. In addition, despite the increase in streamflows, the risk of water deficit may still increase from between 4 and 7 percent to between 7 and 13 percent due to higher agricultural water demand. The simulation results suggest that the reservoir capacity may need to be expanded. In response to the climate change, four strategies are suggested: (1) strengthen flood mitigation measures, (2) enhance drought protection strategies, (3) develop new water resources technology, and (4) educate the public.     

THE IMPACTS OF CLIMATIC CHANGES FOR WATER RESOURCES OF THE COLORADO AND SACRAMENTO-SAN JOAQUIN RIVER BASINS1

ABSTRACT: A wide variety of regional assessments of the water-related impacts of climatic change have been done over the past two decades, using different methods, approaches, climate models, and assumptions. As part of the Water Sector research for the National Assessment of the Implications of Climatic Variability and Change for the United States, several major summaries have been prepared, looking at the differences and similarities in results among regional research projects. Two such summaries are presented here, for the Colorado River Basin and the Sacramento River Basin. Both of these watersheds are vitally important to the social, economic, and ecological character of their regions; both are large snowmelt-driven basins; both have extensive and complex water management systems in place; and both have had numerous, independent studies done on them. This review analyzes the models, methods, climate assumptions, and conclusions from these studies, and places them in the context of the new climate scenarios developed for the National Assessment. Some significant and consistent impacts have been identified for these basins, across a wide range of potential climate changes. Among the most important is the shift in the timing of runoff that results from changes in snowfall and snowmelt dynamics. This shift has been seen in every regional result across these two basins despite differences in models and climate change assumptions. The implications of these impacts for water management, planning, and policy are discussed.     

NATURAL EROSION RATES AND THEIR PREDICTION IN THE IDAHO BATHOLITH1

ABSTRACT: Natural rates of surface erosion on forested granitic soils in central Idaho were measured in 40 m² bordered erosion plots over a period of four years. In addition, we measured a variety of site variables, soil properties, and summer rainstorm intensities in order to relate erosion rates to site attributes. Median winter erosion rates are approximately twice summer period rates, however mean summer rates are nearly twice winter rates because of infrequent high erosion caused by summer rainstorms. Regression equation models and regression tree models were constructed to explore relationships between erosion and factors that control erosion rates. Ground cover is the single factor that has the greatest influence on erosion rates during both summer and winter periods. Rainstorm intensity (erosivity index) strongly influences summer erosion rates, even on soils with high ground cover percentages. Few summer storms were of sufficient duration and intensity to cause rilling on the plots, and the data set was too small to elucidate differences in rill vs. interrill erosion. The regression tree models are relatively less biased than the regression equations developed, and explained 70 and 84 percent of the variability in summer and winter erosion rates, respectively.     

THE EFFECTS OF MINE ACID ON THE POND RIVER WATERSHED IN WESTERN KENTUCKY1

ABSTRACT: H₂SO₄ (sulfuric acid) is formed by a chemical process that occurs in unreclaimed coal mines. The highly toxic acid then flows into the lower swamp areas where it causes considerable damage to the ecosystem. The major effect of the acid is the mass destruction of thousands of trees and various other phreatophytic plants. The contamination is so serious that most of the wildlife has migrated out of the affected area of the swamp in order to survive. Certain geological features such as coal bearing monadanocks make the area somewhat sensitive to mining activities and related geologic hazards. New methods of mine acid abatement make the concept of mass reclamation more realistic than at any time in the past. The constant annihilation of swamp life and processes emphasizes the urgent need for reclamation of the swamp.     

CALIBRATION OF STORM LOADS IN THE SOUTH PRONG WATERSHED,FLORIDA, USING BASINS/HSPF1

ABSTRACT: The South Prong watershed is a major tributary system of the Sebastian River and adjacent Indian River Lagoon. Continued urbanization of the Sebastian River drainage basin and other watersheds of the Indian River Lagoon is expected to increase runoff and nonpoint source pollutant loads. The St. Johns River Water Management District developed watershed simulation models to estimate potential impacts on the ecological systems of receiving waters and to assist planners in devising strategies to prevent further degradation of water resources. In the South Prong system, a storm water sampling program was carried out to calibrate the water quality components of the watershed model for total suspended solids (TSS), total phosphorous (TP), and total nitrogen (TN). During the period of May to November 1999, water quality and flow data were collected at three locations within the watershed. Two of the sampling stations were located at the downstream end of major watercourses. The third station was located at the watershed outlet. Five storm events were sampled and measured at each station. Sampling was conducted at appropriate intervals to represent the rising limb, peak, and recession limb of each storm event. The simulations were handled by HSPF (Hydrologic Simulation Program‐Fortran). Results include calibration of the hydrology and calibration of the individual storm loads. The hydrologic calibration was continuous over the period 1994 through 1999. Simulated storm runoff, storm loads, and event mean concentrations were compared with their corresponding observed values. The hydrologic calibration showed good results. The outcome of the individual storm calibrations was mixed. Overall, however, the simulated storm loads agreed reasonably well with measured loads for a majority of the storms.     

APPLICATION OF THE BASINS DATABASE AND NPSM MODEL ON A SMALL OHIO WATERSHED1

ABSTRACT: The purpose of this study was to evaluate the Better Assessment Science Integrating Point and Nonpoint Sources (BASINS) watershed management system. BASINS data were used with the NPSM model to predict discharge and sediment concentrations at the outlet of a 103 km² Ohio watershed. It was concluded that the NPSM model should always be calibrated but only a few of the parameters provided with BASINS needed to be calibrated. For a three‐year study period, there was a 2 percent underestimation of discharge using area weighted precipitation values and a 25 percent overestimation using the single station data in BASINS. A comparison of observed and predicted monthly discharge resulted in an r² of 0.86 with area‐weighted precipitation and an r² of 0.74 with the single station data. Calibrating the model to substantially improve sediment predictions was unsuccessful and we concluded that a calibration period of one year was too short. For the three‐year study period, the r² for sediment was 0.36 with a slope of 0.37 and an intercept of 18.8 mg/l. The mean observed and predicted sediment concentrations were 27.1 mg/l and 22.6 mg/l, respectively.     

SIMULATION AND DECISIONMAKING: THE PLATTE RIVER BASIN IN NEBRASKA1

Substantial conflict exists over water management and allocation in the Platte River Basin of Nebraska. An interdisciplinary computer simulation model, representing the water quantity, water quality, environmental, and economic dimensions of the conflict, was developed in order to analyze the tradeoffs among allocation scenarios. Most importantly, decisionmakers and interest groups were involved in model development. Simulation results for a base case and two scenarios are presented. One scenario favors protection of instream flow for wildlife; the other favors water diversions for agriculture. Impacts of the instream flow scenario, as measured by the amount of land irrigated, groundwater levels, the amount of wildlife habitat for cranes and catfish, and net agricultural benefits did not differ greatly from those of the base case. However, impacts of the diversion scenario were substantial. On the negative side, instream flows and wildlife habitat declined an average of 39 percent; while, on the positive side, groundwater levels and net agricultural benefits each increased 6 percent. The modeling process was successful insofar as it promoted an understanding among the highly diverse interest groups of the systems nature of the Basin. One agreement on a water diversion schedule among three of the parties has been reached, partly as a result of this process. More comprehensive compromises have not yet been forged. Our experience, however, indicates that modeling success at the policymaking level depends more on the extent to which the policymakers understand the model than it does on model sophistication.     

AN OPERATIONAL WATERSHED MODEL: STEP 1-B: REGULATION OF WATER LEVELS IN THE KISSIMMEE RIVER BASIN1

Step-IB in the first phase of an “Operational Watershed Model” recently initiated by the Central and Southern Florida Flood Control District for managing its water resources is to compute water surface elevation, spatially and temporally, in the Kissimmee River Basin system of reservoirs, channels and spillways. An approach is based upon the principles of gradually varied flow. Mathematical relationships to compute lake stage as a function of storage, and to compute discharge through the control structures as a function of gate opening and differential head across the structures are developed. Their feasibility for application is clearly demonstrated by the simulated mean daily water surface elevation for a period of two years on the tail side of one typical gated spillway and on the head side of another gated spillway.     

POTENTIAL ECONOMIC IMPACTS OF CHANGES IN WATER AVAILABILITY ON AGRICULTURE IN THE TRUCKEE AND CARSON RIVER BASINS,NEVADA, USA1

ABSTRACT: Effects of climate change are likely to be detected in nearly all sectors and regions of the economy, with both winners and losers. One of the consequences of climatic changes could be altered regional water supplies. This paper presents an investigation of regional agricultural implications of changes in water availability. Specifically, using a profit maximization approach, the economic consequences of altered water availability in the Great Basin of Nevada are analyzed in terms of the effects on net returns of agricultural producers. Under the scenarios analyzed in this paper, it is found that with adequate water systems, increase in streamflow and consequent increase in water availability could significantly benefit agricultural producers of this region. Net returns to irrigators could increase by 8 to 13 percent, not taking into account the possibility of changes in crop yields and prices. It is also shown that the benefits from increased water availability are sensitive to likely crop yield and price changes. The potential for adverse effects of climatic changes on water supply is also considered by analyzing the effects of decreased water availability. Under decreased water availability scenarios, farmer net returns decrease substantially.     

EFFECT OF WATERSHED SUBDIVISION ON SWAT FLOW,SEDIMENT, AND NUTRIENT PREDICTIONS1

ABSTRACT: The size, scale, and number of subwatersheds can affect a watershed modeling process and subsequent results. The objective of this study was to determine the appropriate level of subwatershed division for simulating flow, sediment, and nutrients over 30 years for four Iowa watersheds ranging in size from 2,000 to 18,000 km² with the Soil and Water Assessment Tool (SWAT) model. The results of the analysis indicated that variation in the total number of subwatersheds had very little effect on streamflow. However, the opposite result was found for sediment, nitrate, and inorganic P; the optimal threshold subwatershed sizes, relative to the total drainage area for each watershed, required to adequately predict these three indicators were found to be around 3, 2, and 5 percent, respectively. Decreasing the size of the subwatersheds below these threshold levels does not significantly affect the predicted levels of these environmental indicators. These threshold subwatershed sizes can be used to optimize input data preparation requirements for SWAT analyses of other watersheds, especially those within a similar size range. The fact that different thresholds emerged for the different indicators also indicates the need for SWAT users to assess which indicators should have the highest priority in their analyses.