Grantee Research Project Results
Final Report: Integrating Modeling and Management of Agriculturally-Impacted Watersheds, Issues of Spatial and Temporal Scale
EPA Grant Number: R825290Title: Integrating Modeling and Management of Agriculturally-Impacted Watersheds, Issues of Spatial and Temporal Scale
Investigators: Brezonik, Patrick L. , Perry, James A. , Smith, Richard C. , Fang, Andrew F. , Gowda, Prasanna H. , Birr, Adam S. , Easter, K. William , Gleason (Dovciak), Anne , O'Connor, Ben , Dalzell, Brent , Wheeler, Daniel , Mulla, David , Davis, David , Tidwell, Jason , Bell, Jay , ZumBerge, Jeremy , Westra, John , Marr, Kara , Brooks, Kenneth , Olson, Kent , McCann, Laura , Mathews, Leah , Hatch, Lorin , Gerlach, Luther , Talmadge, Philip , Johansson, Robert
Institution: University of Minnesota
EPA Project Officer: Packard, Benjamin H
Project Period: October 1, 1996 through September 30, 1999 (Extended to March 31, 2001)
Project Amount: $813,085
RFA: Water and Watersheds Research (1996) RFA Text | Recipients Lists
Research Category: Watersheds , Water
Objective:
The main objective of our study was to improve understanding of how biophysical and socioeconomic variables interact in agricultural watersheds of varying scales (sizes) and landscape conditions to affect export of nutrients and their effects on in-stream biological communities. In particular, we focused on evaluating the usefulness of agroecoregions?landscape units roughly comparable in size to major watersheds? in understanding and managing nutrient pollution in large, agricultural drainage basins. A second objective was to assess the role of scientific knowledge about the above issues in decisionmaking processes affecting local-level land-use management.
This project took a multidisciplinary approach to study the spatial and temporal scales at which landscape and socioeconomic factors influence water quality degradation in the Minnesota River Basin (MRB). We hypothesized that the optimum scale to understand and manage degradation of water quality, aquatic habitats, biotic integrity, and the socioeconomic factors affecting them occurs within agroecoregion boundaries, rather than watershed boundaries. The hypothesis was tested through hierarchical sampling of soil properties, chemical water quality, aquatic habitat, and aquatic biota. In addition, we conducted stakeholder surveys, computer modeling, and statistical evaluations of long-term stream, lake, and groundwater quality data.
Agroecoregions are landscape units with relatively uniform crop productivity, climate, geologic parent material, soil drainage, and slope steepness; large watersheds generally are composed of two or more agroecoregions. We found that the variance in soil erosion, stream biotic habitat, stream water quality, lake water quality, and groundwater quality was smaller within agroecoregion boundaries than within watershed boundaries. Through linked biophysical and economic modeling, we found that the economic costs of reducing phosphorus loads to streams were lower when best management practices (BMPs) were targeted to specific agroecoregions compared with an untargeted strategy involving entire watersheds. We developed an eight-step framework for restoring and managing watersheds that includes specific steps for defining agroecoregions, prioritizing pollutant loads, and identifying BMPs for each agroecoregion. Finally, we developed a manual describing agroecoregion-specific BMPs to be used in reducing pollutant loads to the MRB. We suggest that watershed management in highly agricultural watersheds will be most effective when watershed boundaries are complemented by agroecoregions to identify and target regions where specific combinations of BMPs for agricultural sediment, nitrogen, and phosphorus abatement are most appropriate.
Summary/Accomplishments (Outputs/Outcomes):
Results and research products were obtained at three levels of inquiry and analysis: (1) technical, discipline-based studies in the following fields: anthropology, applied economics, aquatic chemistry, landscape geography, stream ecology/limnology, and soil science; (2) multidisciplinary technical studies involving two or more of the above fields in concert; and (3) highly interdisciplinary studies aggregating the biophysical and socioeconomic components of the project to produce integrative analyses related to issues of scale in management of agricultural watersheds.
Discipline-Based and Multidisciplinary Technical Studies
Economics. Based on an enviroeconomic modeling analysis, we found that it is more cost-effective to reduce nonpoint pollution by targeting particular regions or practices in a watershed compared with not targeting. Specifically, appreciable reduction in phosphorus nonpoint pollution can occur for: (1) producers farming on crop land susceptible to erosion in close proximity to water who switch from conventional tillage to conservation tillage; and (2) producers who reduce phosphorus fertilization levels to those recommended by the state extension service. Efforts to target those producers could minimize potential losses in farm income in the watersheds and the river basin.
Based on surveys and interviews conducted to explore the magnitude of transaction costs in the context of potential strategies to reduce agricultural phosphorus pollution of the Minnesota River, we found that the most acceptable policies for farmers were a requirement for conservation tillage on highly erodible land and educational programs on BMPs. The least acceptable policies for farmers were a tax on phosphate fertilizers and a tax on manure. Expected farmer resistance to specific strategies was more important as a policy preference determinant of agency personnel than were either farmer costs or administrative costs. A requirement for conservation tillage on highly erodible land was the preferred policy among agency personnel, and a tax on manure was their least preferred policy. Estimated transaction costs associated with four policies to reduce agricultural phosphorus pollution in the Minnesota River were as follows: tax on phosphate fertilizers ($0.94 million); educational programs on BMPs ($3.1 million); requirement for conservation tillage on all cropped land ($7.85 million); and expansion of the permanent conservation easement program ($9.37 million).
Analysis of a separate survey of farmers showed that they are more apt to adopt conservation tillage if they: (1) are larger, (2) are more concerned about erosion on their land, (3) have made a recent major investment in the farm, (4) use other producers for tillage information, (5) have the management skill for conservation tillage, and (6) believe conservation tillage will fit with their production goals and the physical setting of their farm. Some 11 variables often listed as potentially important factors were not found to be important in this survey. These include the long-term viability of the farm; age, education, and experience of the farmer; debt level of the farm; proportion of land rented; complexity of conservation tillage practices; the producer's planning horizon; risk of negative returns; and the quality of conservation tillage information.
Two models were used to estimate the value of improving water quality in the Minnesota River from a 40 percent reduction in phosphorus loading: a contingent-valuation model using stated preference data, and a panel model incorporating both stated and revealed preference data. Results of the contingent valuation model indicated that respondents were willing to pay an average of $10.44 in increased state income taxes per household, and an average of $10.83 per household in water bill surcharges annually for a 40-percent reduction in phosphorus pollution in the Minnesota River. The panel model incorporating stated and revealed preference data yielded an individual value of the same water quality improvement of $38.88.
Stream Ecology. Using macroinvertebrate and stream habitat data from 68 tributaries among three major watersheds and two agroecoregions, we evaluated the effectiveness of these alternative landscape classification systems in explaining variance in habitat and macroinvertebrate metrics, and we also analyzed the relative influence of local habitat versus regional characteristics on macroinvertebrate metrics. Macroinvertebrate community composition and integrity were found to be most strongly influenced by local habitat, and the variance in habitat conditions was best explained at the scale of intersection of major watershed and agroecoregion. The results are consistent with findings of others that most variation in macroinvertebrate community data in large agricultural catchments is attributable to local physical conditions. The results also suggest that BMPs calibrated using information from both watersheds and agroecoregions may lead to better water quality and habitat conditions.
The importance of local stream conditions on fish communities also was established based on a survey of fish, in-stream habitat, and physical stream conditions along 29 reaches of agricultural streams in the MRB and Red River of the North Basin. Fifty-four species of fish from 13 families were collected. Principal component analysis identified six variables (percent run, percent boulder, percent woody debris, percent overhanging vegetation, percent sand, and the frequency of erosion) that explained 79 percent of the variability of in-stream habitat and physical conditions. Managers of warm-water streams need to consider local stream features in developing management or restoration plans. Although watershed-scale restoration is important to improve water quality conditions, local considerations are essential for restoring or enhancing fish communities.
The influence of riparian cover and basin runoff potential on benthic invertebrate communities was investigated in streams of the MRB. Streams with wooded riparian cover had significantly higher invertebrate community index scores and numbers of depositional taxa, and lesser proportions of shredders and Chironomini (Diptera: Chironomidae) than open streams. Streams with low runoff potential basins had greater proportions of Ephemeroptera-Plecoptera-Trichoptera (EPT) and collectors, and lower Hilsenhoff Biotic Index (HBI) scores than streams with high runoff potential basins. Basin-level land use did not significantly influence the variance explained by riparian cover and basin runoff potential. Riparian characteristics, channel structure, and hydrology were significantly different between wooded and open sites, suggesting that invertebrate communities are constrained by these local factors. Based on analysis of 58 second- and third-order streams in the Blue Earth, Le Sueur, and Lower Minnesota watersheds, we found that the intersection of agroecoregions and major watersheds was a successful predictor of fish community composition. It is clear that the scale of agroecoregion-watershed intersections is an appropriate alternative to simple use of watersheds to predict and manage fish communities in streams. However, there are many confounding variables that remain to be tested before we precisely understand the variables that control fish community composition in heavily impacted agricultural streams.
Aquatic Chemistry. Water, suspended sediment, and soil samples were collected during the summers of 1999 and 2000 across the MRB during "typical summer runoff events" to assess spatial water quality and characterize the suspended sediments by agroecoregions. Average values for water quality parameters showed large standard deviations, often found in large-scale assessments, within each of the 13 major agroecoregions. Reducing the spatial scale to the overlap of the agroecoregions and the 12 major watersheds of the MRB produced more noticeable trends when rainfall and stream size were considered. The main tributaries of the Minnesota River showed almost no lag time between peak flows and peak concentrations with similar magnitudes in the concentrations. Drainage ditches and other small-ordered streams showed high fluctuations in concentration magnitudes.
The trace and minor element composition, mineralogy, and particle-size distribution of soil and suspended sediment samples were measured to develop a "fingerprinting" procedure to partition the source of suspended solids in river water between stream bank erosion and loss of top soil from agricultural land in the basin. This technique we derived used multivariate statistical analysis primarily of the trace and minor elemental composition of suspended solids samples and similar analyses of stream bank and agricultural soils from the basin. The suspended sediment of rivers within the MRB is mostly clay-sized particles (mean diameters of 15 to 25 m) with ~13 percent by mass being volatile. Elemental composition of the sediment is mostly that found in aluminosilicate clays Al, Ca, Mg, Fe, Na, K, P, and Si, with trace quantities of Ba, Co, Cr, Li, Mn, Pb, Rb, Ti, and Zn. Suspended solids source attribution based on fingerprinting indicated that most of the suspended solids in river samples were derived from agricultural soils, but a substantial fraction also was attributed to stream bank erosion.
Soil Science and Landscape Analysis. The applicability of a field-scale phosphorus site index (PSI) to regional-scale assessment of P loss vulnerability was evaluated using Minnesota watersheds. The results suggest that concepts used to assess potential P movement at the field scale can be discerned on a regional scale given certain modifications to accommodate for the generalized nature of the input data. Relationships between long-term monitoring data and PSI ratings suggest that the modified PSI effectively ranked watersheds based on potential for P movement to surface water bodies.
Regional trends in lake and groundwater quality were evaluated using four different land classification approaches: major land resource areas, ecoregions, agroecoregions, and hydrologic units. Based on a combination of statistical and spatial evidence, ecoregions and agroecoregions depict relatively homogenous patterns in lake water quality intraregionally. Distinct areas of NO3- contamination were identified using the agroecoregion classification system. The findings are useful to natural resource managers to establish regionally specific water quality goals and prioritize the use of funds in regions that are most vulnerable to water quality degradation.
Soil spatial variability at multiple scales and the optimum scales at which to study landscape processes affecting these variations were evaluated in the MRB using analysis of variance and geostatistical methods. We determined the predominant scale(s) of influence on soil property variations within the MRB, quantified relationships between landscape position and soil properties, and determined the effects of scaling soils data to smaller scales. Surface horizon pH, a horizon thickness, depth to CaCO3, and Profile Darkness Index (PDI) were the soil morphological properties analyzed across a climosequence of soils to assess spatial variability. Results indicate that most of the variability in soil properties in the MRB occurs at the largest scale (smallest spatial unit) sampled (field-scale). As precipitation decreases from east to west in the Basin, soil property variability became more variable across a hillslope transect, indicating the large influence of water movement on variability of soil properties. Soil-landscape relationships at all scales showed that PDI is well correlated with landscape position in the MRB, which suggests soil-landscape modeling may be useful for soil mapping. Implicit representation of soil variability decreased as data were aggregated from field-collected information to county-level soil surveys, but they remained fairly consistent between county-level soils data and general soil associations of the State Soil Geographic (STATSGO) database. Soil variability assessment by traditional soil survey techniques may not adequately represent the variability to the users. Hierarchical quantitative sampling and analysis techniques are proposed to assess soil variability at the largest scales (smallest spatial units), and extrapolation of this information to the greater landscape can be accomplished by soil-landscape modeling.
We used the Agricultural Drainage and Pesticide Transport (ADAPT) simulation model to evaluate the relative effects of nitrogen application rate, tile-drain spacing, and tile-drain depth on NO3- losses through tile drains for conditions that are typical of the upper Midwest. ADAPT, a daily time-step continuous water table management model, was calibrated and validated for tile drainage and associated NO3- losses using long-term monitoring data measured on three experimental plots near Waseca in the MRB. Soils at the sites were a Webster clay loam (fine-loamy, mixed, superactive, mesic Typic Endoaquoll) under continuous corn (Zea mays L.) with conventional tillage treatment. For the calibration period, the model predicted mean monthly tile drainage and NO3--N losses of 4.6 cm and 6.7 kg ha-1, respectively, against measured tile drainage; and NO3--N losses of 4.6 cm and 6.9 kg ha-1, respectively. For the validation period, the predicted mean monthly tile drainage and NO3--N losses were 4.0 cm and 6.1 kg ha-1, respectively, against measured tile drainage; and NO3--N losses of 3.7 cm and 6.5 kg ha-1, respectively. Long-term simulations were made for a wide range of climatic conditions between 1915 and 1996 to evaluate the effect of drain spacing, drain depth, and N application rates on tile drainage and NO3- losses. Simulation results indicate that much greater reductions in NO3- losses occur with reduced N application rates than with increases in drain spacing or decreases in drain depth.
ADAPT also was used to evaluate the impact of agricultural nonpoint source pollution in the Lower Minnesota River Basin (LMRB). Spatial data layers of land cover, slope, tillage practice, and soils information were overlaid with Geographic Information System (GIS) to create model input data. Land cover and tillage practice information were derived from remotely sensed data, and soils data were extracted for STATSGO map units. Additional model inputs, such as crop and climatic data, were obtained from local and national databases and interviews with local experts. Observations from six gauged tributaries in the LMRB were used to calibrate the model. Comparison of predicted and observed monthly flow data from the six gauged watersheds in the LMRB gave agreement ranging from 0.36 to 0.85 (r2 values). Comparison of predicted and observed monthly sediment and nitrate loading gave agreement (r2 values) ranging from 0.22 to 0.71 and from 0.19 to 0.78, respectively. The model performed well for the southeastern and western portions of the LMRB, where land use is dominated by agriculture, but performance decreased in the north-central and northeastern portions of the LMRB, which transitions to mixed and urban land use with little land devoted to agriculture. This suggests that ADAPT is best suited for agriculturally dominated watersheds.
The calibrated model was used to simulate monthly flow, sediment, and nitrate from ungauged watersheds in the LMRB. The model also was used to evaluate alternative agricultural management practices such as conservation tillage, conversion of cropland to pasture, increased subsurface tile drainage, and changes in N-fertilizer application rates and timing. Results indicate that a 20-percent reduction in N-fertilizer accompanied by springtime application could reduce nitrate loads from agricultural watersheds by up to 7.4 percent. An increase in adoption of conservation tillage (75 percent more than current levels) could reduce sediment load by up to 43 percent. However, increased adoption of conservation tillage also produced slight increases in flow and nitrate loading. When 75-percent adoption of conservation tillage was accompanied by 10-percent conversion of cropland to pasture, up to 51-percent reductions occurred in sediment loads, and nitrate loads were reduced slightly. A 50-percent increase in areas modified by subsurface tile drainage in the western LMRB increased nitrate loading and flow up to 46 and 12 percent, respectively, and decreased sediment loading up to 15 percent. Reductions in nitrate loading realized by changes in N-fertilizer management practices thus may be offset by adoption of other management practices such as conservation tillage and addition of new (or repair of existing) subsurface tile drainage lines.
Measurement of soil algal bioavailable phosphorus (aBAP) and the identification of soils with high risk of P loss are two key points in controlling eutrophication of water bodies in agricultural areas. We examined these points for 24 soils sampled across the MRB. To find a suitable surrogate for the lengthy algal bioassay procedure of aBAP test, results from various soil P testing procedures were evaluated against bioassay-determined aBAP values. Results showed that for MRB soils, which are generally calcareous, P levels measured by Melich III extraction, NaOH-NaCl extraction, and Fe-oxide impregnated paper methods all were significantly correlated with bioassay-determined aBAP values (r2 = 0.65, 0.62, 0.68, respectively; all p < 0.001), suggesting the feasibility of estimating aBAP with these extraction methods in MnRB. P sorption maxima of the soils were determined by the Langmuir sorption model. PSI, an indicator of the potential of a soil to release P to runoff, was calculated by dividing soil P level by soil P sorption maximum. Results indicated that PSI was closely correlated to soil Bray-P level (r2 = 0.79), which is widely used in the MRB to estimate crop-available P. Therefore, it may be possible to use Bray-P to estimate the P loss potential of a soil. In contrast, chemical and physical properties of the soils, such as pH, organic matter content, calcium carbon equivalent, and clay content, failed to provide adequate information in estimating aBAP and soil P sorption maximum for the soils in MnRB, which made it difficult to use these soil properties to evaluate soil P loss potentials.
Laboratory runoff experiments conducted in 0.61 m x 0.15 m x 0.10 m boxes measured the bioavailable P (BAP) content of runoff from 10 calcareous soils from the MRB under simulated storms (30-minute rain events at 6 cm h-1). The soluble reactive P (SRP) concentration in runoff was related to Mehlich III-P (r2 = 0.96, p < 0.001), Olson-P (r2 = 0.95, p < 0.001), and NaOH-P (r2 = 0.81, p < 0.001) of the surface soils. A linear relationship (r2 = 0.88, p < 0.001) was obtained between the concentration of SRP in runoff and an index of P soil sorption saturation (PSI-s) calculated using sorptivity as the measure of the inherent soil P sorption capacity. SRP in runoff also was related (r2 = 0.89, p < 0.001) to the equilibrium P concentration (EPC) of the surface soils (as determined from the Langmuir sorption model). BAP levels in runoff, estimated by the Fe-oxide impregnated paper method, were well predicted by Mehlich III-P, NaOH-P, EPC, and PSI-s of the surface soils, but correlation coefficients between these variables and runoff BAP were generally lower than those for runoff SRP. Soil Fe-paper-P and the chlorophyll response of soils (from algal bioassays) had higher correlations with runoff BAP than with runoff SRP.
These findings provide tools to develop simple and rapid methods to predict BAP levels in agricultural runoff. On the practical side, we related physical and chemical characteristics of soil to its BAP loss potential. If a general relationship can be established between soil P sorption saturation and runoff P concentration, watershed managers will have a tool for tailoring management practices to meet the specific needs of individual fields or farms according to their soil and hydrological conditions. Likewise, when the interaction of stream sediment and DRP are fully described, standards for allowable DRP concentration in streams can be set to prevent excessive release of BAP into downstream water bodies.
Integrated Studies
Watershed management is trapped between two conflicting trends: science is demonstrating the need to consider more coarse spatial scales and longer temporal scales, but decisionmaking is becoming more localized and site-specific. In particular, effective management of watersheds and water resources requires that managers understand the implications of their actions throughout a wide range of spatial and temporal scales, but these managers must accept the fact that decisionmaking around the world is shifting towards finer, more local scales. The latter situation reflects a worldwide trend of more collaborative approaches to decisionmaking that involve increasing public participation. We describe the conflict between these two conditions as the scale incompatibility dilemma. This dilemma poses a significant constraint on decisionmaking for water quality management in large watersheds and drainage basins. We describe the historical basis for the dilemma and provide illustrations of it in the MRB. Managing landscapes or environments comprehensively while still incorporating the unique requirements of local biophysical resources and communities thus is an inherently challenging process. From a sociological perspective, the dilemma exemplifies the conflict between what Gerlach has termed ecosystemic and ethnolocal imperatives. Although the dilemma is widely recognized, at least implicitly, solutions to the problem have not been widely developed, but such solutions of necessity will involve compromises between top-down, highly centralized management that at the extreme approaches autocratic decisionmaking and completely decentralized management that in the extreme could lead to complete chaos.
The Minnesota River (Minnesota, USA) receives large nonpoint source pollutant loads. Complex interactions among agricultural, state agency, and environmental groups, and issues of scale make watershed management difficult. The watershed management framework is prevalent today because land use in these basic hydrologic units is presumed to be reflected in receiving stream water quality. However, landscape characteristics affecting soil erosion and water quality (e.g., precipitation, geomorphology, slope, soil internal drainage, cropping system) often vary significantly within a single large watershed (> ~2000 km2). A strategy of requiring uniform watershed BMPs across such a watershed would not account for this variability, and would not be satisfactory for soil conservation, water quality, or socioeconomic returns. It also is unlikely that stream water quality monitoring will take place on enough small streams within a large watershed to capture the landscape variation. Based upon empirical data from the MRB, we developed agroecoregions to quantify this variation. Subdividing the basin's 12 major watersheds into agroecoregions based on soil type, geology, steepness, and climate enhances predictability of stream water quality parameters. This approach can help target cleanup efforts to the most sensitive soils and landscapes within the most critical watersheds. Our work has shown that soil erodibility index variability, stream biotic habitat scores, and some chemical indicators of water quality were better represented by agroecoregions or by areas defined by the intersections of agroecoregions and major watersheds than by major watersheds alone. In contrast, agroecoregions explained little of the variance in social and economic variables.
Nonetheless, stakeholder characterization and economic analyses revealed a large variance in attitudes and beliefs about pollution issues and mitigation costs across the MRB, due in part to problems of scale perception. We suggest that watershed management in highly agricultural watersheds will be most effective when watersheds are complemented by agroecoregions to identify and target regions where specific combinations of BMPs for agricultural sediment and nutrient abatement are most suited.
Many managerial frameworks and strategies have been proposed for managing and/or maintaining watershed resources. Nonpoint source pollutants are of concern in highly agricultural areas, and watershed management in these areas provides unique opportunities and challenges. The MRB provided a case study with which to demonstrate the consequences of management decisions in a large, highly agricultural watershed. We developed an eight-step process to aid decisionmakers to identify, assess, and implement restoration measures in agriculturally intensive watersheds. Each step was related to the recent history of the MRB. The eight steps are: (1) problem identification; (2) water quality monitoring; (3) evaluating pollution sources; (4) setting water quality goals; (5) identifying terrestrial ecosystem characteristics that affect water quality; (6) prioritizing watersheds and targeting specific (eco)regions within watersheds; (7) identifying practices and approaches that are cost-effective in improving and/or maintaining water quality; and (8) implementing these strategies and monitoring progress towards goals. Three key elements are emphasized: a specific sequence of events for effective management, the need for stakeholder involvement, and the iterative nature of the process.
This project resulted in a wide range of published and presented work. The graduate students working on the project produced 10 M.S. theses and 6 Ph.D. dissertations. Collectively, we have presented 23 papers to date and have written 20 technical papers on the findings of the project. Of the 20 papers, 12 are published and 8 are in review.
As with most interdisciplinary projects, our more synthetic efforts are based on the disciplinary efforts that preceded them. Of the 43 papers we have presented or written, at least 8 are highly integrative, and many more involved work from two or more disciplines. Our experience suggests that this degree of integration is high for projects of the size and duration as this one. We believe that we were able to achieve this level of integration because our project had a relatively small number of principal investigators who were: (1) committed to the concept of interdisciplinary and integrative work, and (2) experienced in guiding students and seeking integrative messages. In addition, our project employed a postdoctoral research associate who was hired specifically to fill an integrative role, and we built hypotheses that were intended to be synthetic/integrative.
Journal Articles on this Report : 5 Displayed | Download in RIS Format
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Brezonik PL, Easter KW, Hatch L, Mulla D, Perry J. Management of diffuse pollution in agricultural watersheds: lessons from the Minnesota River basin. Water Science and Technology 1999;39(12):323-330. |
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Dovciak AL, Perry JA. In search of effective scales for stream managemetn:does agroecoregion, watershed, or their intersection best explain the variance in stream invertebrate communities? Environmental Management 2002;30(3):365-377. |
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Dovciak AL, Perry JA. Whose watershed is this? A decision case study of agricultural drainage in the Midwestern USA. Journal of Natural Resources and Life Sciences Education 2000;29:95-101. |
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Hatch LK, Mallawatantri A, Wheeler D, Gleason A, Mulla D, Perry J, Easter KW, Smith R, Gerlach L, Brezonik P. Land management at the major watershed-agroecoregion intersection. Journal of Soil and Water Conservation 2001;56(1):44-51. |
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Westra JV, Easter KW, Olson KD. Targeting nonpoint source pollution control: phosphorus in the Minnesota River basin. Journal of the American Water Resources Association 2002;38(2):493-505. |
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Supplemental Keywords:
watersheds, land, soil, sediments, ecological effects, bioavailability, ecosystem restoration, scaling, terrestrial, aquatic, habitat, decisionmaking, public policy, community-based, cost-benefit, nonmarket valuation, contingent valuation, survey, socioeconomic, willingness-to-pay, environmental chemistry, biology, hydrology, limnology, soil science, modeling, monitoring, GIS, Midwest, Minnesota, MN, EPA Region 5, agriculture;, RFA, Scientific Discipline, Toxics, Water, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Hydrology, Nutrients, Water & Watershed, exploratory research environmental biology, Ecosystem/Assessment/Indicators, Chemical Mixtures - Environmental Exposure & Risk, Ecosystem Protection, pesticides, State, Ecological Effects - Environmental Exposure & Risk, Ecological Effects - Human Health, Ecology and Ecosystems, Watersheds, Ecological Indicators, environmental monitoring, fate and transport, nutrient transport, aquatic ecosystem, Minnesota, anthropogenic stress, basin hydrology, agriculturally impacted watershed, ecological exposure, bacteria, watershed management, agricultural watershed, modeling, Midwestern U.S., spatial and temporal scale, aquatic ecosystems, sediment runoffRelevant Websites:
http://www.soils.umn.edu/Research/research5.htm 
Progress and Final Reports:
Original AbstractThe 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.