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Design discharge at a location of interest is conventionally determined using flood frequency analysis, precipitation frequency analysis, or national flood frequency equations. However, none of these three methods can be used to estimate the design discharge for ungauged watershed where high flows are from overflows of the watershed's bordering stream(s), such as the Hartsville Coulee watershed located in northwestern Minnesota. The historical high flows in the Hartsville Coulee were from the overflows of the Red River of the North (RRN). The objective of this study was to set up and use a HEC-RAS hydrodynamic model to determine the maximum overflow rate from RRN into the Hartsville Coulee in 1997, when the record flooding occurred. The model was calibrated using the observed daily streamflows at four US Geological Survey (USGS) gauging stations along RRN. The breach, over which the floodwater was spilled into the Hartsville Coulee in 1997, was defined using the topographic data surveyed by US Army Corps of Engineers (USACE). The results indicated that the maximum overflow rate was likely between 250 and 310 m3 s-1. The computed overflow rate in this study was well compatible with the value estimated by USGS based on a field reconnaissance as well as the value estimated by USACE using Manning equation. In generalization, the HEC-RAS hydrodynamic module can be used to estimate design discharges for overflow-receiving drainage areas such as the Hartsville Coulee watershed. [ABSTRACT FROM AUTHOR]

A remote sensing-based land surface characterization and flux estimation study was conducted using Landsat data from 1997 to 2003 on two grazing land experimental sites located at the Agricultural Research Services (ARS), Mandan, North Dakota. Spatially distributed surface energy fluxes [net radiation (R n), soil heat flux (G), sensible heat (H), latent heat (LE)] and surface parameters [emissivity (ε), albedo (α), normalized difference vegetation index (NDVI) and surface temperature (T sur)] were estimated and mapped at a pixel level from Landsat images and weather information using the Surface Energy Balance Algorithm for Land (SEBAL) procedure as a function of grazing land management: heavily grazed (HGP) and moderately grazed pastures (MGP). Energy fluxes and land surface parameters were mapped and comparisons were made between the two sites. Over the study period, H, ε and T sur from HGP were higher by 6.7%, 18.2% and 2.9% than in MGP, respectively. The study also showed that G, LE and NDVI were higher by 1.3%, 1.6% and 7.4% for MGP than in HGP, respectively. The results of this study are beneficial in understanding the trends of land surface parameters, energy and water fluxes as a function of land management. [ABSTRACT FROM AUTHOR]

Soil data comprise a basic input of SWAT (Soil and Water Assessment Tool) for a watershed application. For watersheds where site specific soil data are unavailable, the two U.S. Department of Agriculture (USDA) soil databases, the State Soil Geographic (STATSGO) and Soil Survey Geographic (SSURGO) databases, may be the best alternatives. Although it has been noted that SWAT models using the STATSGO and SSURGO data may give different simulation results for water, sediment, and agricultural chemical yields, information is scarce on the effects of using these two databases in predicting streamflows that are predominantly generated from melting snow in spring. The objective of this study was to assess the effects of using STATSGO versus SSURGO as an input for the SWAT model's simulation of the streamflows in the upper 45 percent of the Elm River watershed in eastern North Dakota. Designating the model as SWAT-STATSGO when the STATSGO data were used and SWAT-SSURGO when the SSURGO data were used, SWAT-STATSGO and SWAT-SSURGO were separately calibrated and validated using the observed daily streamflows. The results indicated that SWAT-SSURGO provided an overall better prediction of the discharges than SWAT-STATSGO, although both did a good and comparable job of predicting the high streamflows. However, SWAT-STATSGO predicted the low streamflows more accurately and had a slightly better performance during the validation period. In addition, the discrepancies between the discharges predicted by these two SWAT models tended to be larger at upstream locations than at those farther downstream within the study area. [ABSTRACT FROM AUTHOR]

In this study, remotely sensed data and geographic information system (GIS) tools were used to estimate storm runoff response for Simms Creek watershed in the Etonia basin in northeast Florida. Land cover information from digital orthophoto quarter quadrangles (DOQQ), and enhanced thematic mapper plus (ETM+) were analyzed for the years 1990, 1995, and 2000. The corresponding infiltration excess runoff response of the study area was estimated using the U.S. Department of Agriculture (USDA), Natural Resources Conservation Service Curve Number (NRCS-CN) method. A digital elevation model (DEM)/GIS technique was developed to predict stream response to runoff events based on the travel time from each grid cell to the watershed outlet. A comparison of predicted to observed stream response shows that the model predicts the total runoff volume with an efficiency of 0.98, the peak flow rate at an efficiency of 0.85, and the full direct runoff hydrograph with an average efficiency of 0.65. The DEM/GIS travel time model can be used to predict the runoff response of ungaged water-sheds and is useful for predicting runoff hydrographs resulting from proposed large scale changes in the land use. [ABSTRACT FROM AUTHOR]

The use of geographic information systems (GISs) and remote sensing to facilitate the estimation of runoff from watershed and agricultural fields has gained increasing attention in recent years. This is mainly due to the fact that rainfall-runoff models include both spatial and geomorphologic variations. The US Department of Agriculture, Natural Resources Conservation Service Curve Number (USDA-NRCS-CN) method was used in this study for determining the runoff depth. Runoff curve number was determined based on the factors of hydrologic soil group, land use, land treatment, and hydrologic conditions. GIS and remote sensing were used to provide quantitative measurements of drainage basin morphology for input into runoff models so as to estimate runoff response. The study was conducted on the S-65A sub-basin of the Kissimmee River basin in south Florida. Land use from Landsat images for 1980, 1990 and 2000 were considered in the study. The process of determining spatially distributed runoff curve numbers from Landsat images is presented in this study using GIS and image processing software. Spatially distributed runoff curve numbers and runoff depth were determined for the watershed for different land use classes. Results of the study show that land use changes determined from Landsat images are useful in studying the runoff response of the basin. It is shown that the S-65A sub-basin has undergone land use and runoff response changes over the 20 years period of time. The area covered by water and wetlands in 2000 is higher than in 1980 and 1990. In 2000 areas having CN of greater than 90 accounted for 3% compared to 0.9 and 0.6% in 1980 and 1990 respectively. This was due to the increase in wetlands and water covered areas attributed to the Kissimmee River restoration work, which started in 1997 and aimed at restoring lost wetlands and floodplains. [Copyright &y& Elsevier]

This article presents a discussion on the topic "Adapting Existing Models to Examine Effects of Agricultural Conservation Programs on Stream Habitat Quality," by F. Douglas Shields, Jr., Eddy J. Langendoen, and Martin W. Doyle. The authors suggested some strategies for appropriately applying the leveraged approach. The leveraged approach involves conjunctively using several hydrologic models to predict six key habitat quality attributes governing stream habitat quality including watershed land use taken as a model input.

The USDA Soil Conservation Service (SCS) curve number (CN) method has been the foundation of the hydrology algorithms in commonly used continuous simulation models, including the Soil and Water Assessment Tool (SWAT). This expanded use of the SCS-CN method has proven successful for many applications. However, because the SCS-CN method was originally developed to determine design peak discharges of synthetic storm events under an average antecedent moisture condition, research is needed to address the controversy over the use of this method to represent continuous precipitation runoff processes. In addition, poor results obtained for some conditions indicate the necessity to improve the method to provide a more realistic and accurate representation of waterflow amounts, paths, and source areas upon which erosion and water quality predictions depend. Thus, the objectives of this study were to: (1)propose a modified curve number (MCN) method, and (2) assess the MCN method relative to the existing SWAT method with an Ia/S value either equal to 0.2 or 0.05. The equations that formulate the MCN method were coded into the SWAT 2005 framework. A SWAT model implementing the MCN method was evaluated along with the models implementing the existing SWAT method with Ia/S values of 0.2 and 0.05. The evaluation was conducted in the 870 km² upper portion of the Forest River watershed located in northeastern North Dakota. The results revealed that the total streamflows predicted by the three models were comparable, as indicated by similar values for the Nash-Sutcliffe coefficient. However, the MCN approach resulted in the most accurate prediction of the streamflow components (i.e., baseflow versus direct flow) as well as water yields. For the study area, the MCN method was judged to be superior to the existing commonly used curve number methods in terms of mimicking the precipitation runoff processes. [ABSTRACT FROM AUTHOR]