Landscape Models for Simulating Water Quality at Point, Field, and Watershed Scales

Abstract

ABSTRACT. In the last four decades, a plethora of models has been developed to simulate nonpoint-source (NPS) odeling nonpoint-source (NPS) pollutant fate and transport processes across multiple scales is fundamental to addressing a number of environmental and natural resource issues, including degradation of soil and contamination of surface and ground waters. Landscape NPS models are currently used for a variety of purposes, including registration of pesticides and other agrochemicals, designing soil conservation practices, water table management, prevention of chemical pollution of surface water bodies and groundwater, protection of aquatic biota and development of Total Maximum Daily Loads (TMDLs). Virtually all federal agencies currently have their own models or support models developed elsewhere. According to Singh and Woolhiser (2002), "In the years ahead, the models will become even more common and will play an increasing role in our day-to-day lives." Since NPS pollutant transport is mainly driven by meteorological events, the early to mid-20th century saw the development of mathematical descriptions of individual hydrologic components (e.g., infiltration, runoff, evapotranspiration, and interception). The digital revolution of 1960s witnessed the integration of individual hydrologic components (Singh and Woolhiser, 2002) into functional models that can be applied at various spatial and temporal scales. The development of NPS models in the U.S. began in response to the Clean Water Act (Arnold and Fohrer, 2005). Examples of these models include AGNPS (Young et al., 1987), AnnAGNPS (Bingner and Theurer, 2003), ANSWERS Dillaha, 1996, 2000), APEX (Williams and Izaurralde, 2005), CREAMS (Knisel 1980), DRAINMOD (Skaggs, 2007, EPIC (Williams et al., 1984), GLEAMS (Leonard et al., 1987;Knisel and Davis, 1999), GWLF (Haith and Shoemaker, 1987), HSPF (Bicknell et al., 2001), HY-DRUS (Šimůnek et al., 2005, 2006, KINEROS (Woolhiser et al., 1990), LEACHM (Hutson and Wagenet, 1992), MAC-RO (Jarvis, 1994), NLEAP (Shaffer et al., 1991), RUSLE (Renard et al., 1991), RZWQM (Ahuja and Hebson, 1992) , SWAT (Neitsch et al., 2002), and WEPP (Laflen et al., 1991). These models tend to be scale dependent and are usually suited for profile/horizon/pedon (point scale), field/farm (field scale), or watershed scale; however, there are a few exceptions.The land phase of the hydrologic cycle is complicated and includes a great deal of uncertainty (Singh and Woolhiser, 2002) because of the spatial and temporal heterogeneity of soil properties, land use, precipitation, etc. Currently, a model that simultaneously operates at multiple spatial scales does not exist (the hierarchies of scales at which NPS models are M

Effectiveness of best management practices in improving water quality in a pasture-dominated watershed

“…The major components of the SWAT model are climate, hydrologic cycle, sediment, nutrients, pesticide, bacteria, plants, and management. The SWAT model has been widely used to quantify the water quality impacts of various management decisions at various spatial scales, ranging from field and farm level Gollamudi et al 2007;Maski et al 2008;Srivastava et al 2007) to large watersheds (Green et al 2006;Quansah et al 2008;White and Chaubey 2005) and at various temporal scales, ranging from daily to several decades (Heathman et al 2009;Renschler and Lee 2005). More than 250 peer-reviewed journal articles have been published demonstrating the SWAT applications on sensitivity analyses, model calibration, hydrologic analyses, pollutant load assessment, and climate change impacts on hydrology and pollutant losses (Gassman et al 2007).…”

Potential water quality changes due to corn expansion in the Upper Mississippi River Basin

“…We also consider phosphorous as well as nitrogen export, an important addition because, as previously noted, phosphorous is now understood to contribute to hypoxic conditions in the Gulf. Numerous water quality models exist that have been developed for analyzing various environmental problems for specific scales as documented in extensive literature reviews (e.g., Singh 1995, Shepherd et al 1999, Borah and Bera 2003, Borah et al 2006, Srivastava et al 2007, Breuer et al 2008. One of the most widely used of these models is the Soil and Water Assessment Tool (SWAT), a watershed-scale water quality model (Arnold et al 1998, Arnold and Fohrer 2005), which we used in this study both to simulate the UMRB hydrologic balance and to estimate the changes in nutrient (phosphorous and nitrogen) and sediment loadings in response to alternative crop choices and rotation changes.…”

Application of a simple multiplicative spatio-temporal stream water quality model to the river Conwy, North Wales

“…The combination of class groups used in the landscape 9 definition is shown in Table 3. 10 This choice of grouping is also supported by evidence from other studies of enhanced 2 atmospheric deposition of some water quality variables, differences in soil processes in 3 different soil types, particularly between peat and mineral soils, and the strong 4 association between water quality and farming, where the fertility of the soil is 5 artificially influenced by farming practices 12,21,11 . 6 7 The three classifications do not explicitly include a number of covariates which are likely 8…”