Evaluating Hydrologic Response of an Agricultural Watershed for Watershed Analysis

Manoj Kumar Jha

doi:10.3390/w3020604

Abstract

This paper describes the hydrological assessment of an agricultural watershed in the Midwestern United States through the use of a watershed scale hydrologic model. The Soil and Water Assessment Tool (SWAT) model was applied to the Maquoketa River watershed, located in northeast Iowa, draining an agriculture intensive area of about 5,000 km2. The inputs to the model were obtained from the Environmental Protection Agency’s geographic information/database system called Better Assessment Science Integrating Point and Nonpoint Sources (BASINS). Meteorological input, including precipitation and temperature from six weather stations located in and around the watershed, and measured streamflow data at the watershed outlet, were used in the simulation. A sensitivity analysis was performed using an influence coefficient method to evaluate surface runoff and baseflow variations in response to changes in model input hydrologic parameters. The curve number, evaporation compensation factor, and soil available water capacity were found to be the most sensitive parameters among eight selected parameters. Model calibration, facilitated by the sensitivity analysis, was performed for the period 1988 through 1993, and validation was performed for 1982 through 1987. The model was found to explain at least 86% and 69% of the variability in the measured streamflow data for calibration and validation periods, respectively. This initial hydrologic assessment will facilitate future modeling applications using SWAT to the Maquoketa River watershed for various watershed analyses, including watershed assessment for water quality management, such as total maximum daily loads, impacts of land use and climate change, and impacts of alternate management practices.

Highlights

Hydrology is the main governing backbone of all kinds of water movement and of water-related pollutants
The model was found to explain at least 86% and 69% of the variability in the measured streamflow data for calibration and validation periods, respectively. This initial hydrologic assessment will facilitate future modeling applications using Soil and Water Assessment Tool (SWAT) to the Maquoketa River watershed for various watershed analyses, including watershed assessment for water quality management, such as total maximum daily loads, impacts of land use and climate change, and impacts of alternate management practices
Understanding the hydrology of a watershed and modeling different hydrological processes within a watershed are very important for assessing the environmental and economical well-being of the watershed

Summary

Introduction

Hydrology is the main governing backbone of all kinds of water movement and of water-related pollutants. Simulation models of watershed hydrology and water quality are extensively used for water resources planning and management. These models can offer a sound scientific framework for watershed analyses of water movement and provide reliable information on the behavior of the system. New developments in modeling systems have increasingly relied on geographic information systems (GIS) that have made large area simulations feasible, and on database management systems such as Microsoft Access to support modeling and analysis. Models can save time and money because of their ability to perform long-term simulations of the effects of watershed processes and management activities on water quantity, quality, and on soil quality [1]

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