Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/11/2003
Publication Date: 10/20/2003
Citation: Harmel, R.D., King, K.W., Richardson, C.W., Williams, J.R. 2003. Long-term precipitation analyses for the Central Texas Blackland Prairie. Transactions of the American Society of Agricultural Engineers. 46(5):1381-1388. Interpretive Summary: Knowledge of rainfall properties allows decision makers to best utilize the occurrence of natural rainfall events because rainfall ultimately determines surface and groundwater supplies. Therefore, knowledge of historical rainfall patterns is necessary to make informed decisions and predictions about future water supplies for agricultural, industrial, ecological, and domestic needs. In the Texas Blackland Prairie, an important agricultural region with a large and increasing urban population, drought and excess rainfall can be experienced throughout the year. With the diverse demands placed on water resources in this region and an increasing demand resulting from an increasing population, water resource management will be an even more important issue in the future. Faced with these demands, the continuous rainfall record from the USDA-ARS Grassland Soil and Water Research Laboratory watersheds near Riesel, TX, should provide valuable information on long-term trends in rainfall intensity, frequency, and amounts.
Technical Abstract: Continuous records of intensively monitored precipitation data are rare, but where available they provide valuable regional information on hydrologic structure design and on other water supply and water quality management and modeling issues. One such long-term precipitation record exists for the Texas Blackland Prairie region. Beginning in 1937 and continuing to the present, hydrologic data have been collected at the USDA-ARS Grassland Soil and Water Research Laboratory watershed facility near Riesel, TX. The objectives of this paper are to present long-term analyses and to publicize the availability of that precipitation database. Long-term analyses included examination of general precipitation properties, depth-duration-frequency relationships, and trends in rainfall amount and occurrence. Annual rainfall for the region averages about 890 mm with relatively wet springs and falls and drier summer and winter months. Depth-duration-frequency results emphasize the need for engineers to use the most current and extensive data sets and/or proven relationships in design of hydrologic structures. Several significant temporal trends, which potentially will affect water resource management, were also determined. These trends include increases in October rainfall, non-spring rainfall, and the number of summer and fall rainy days. These increases, however, are offset to some degree by decreases in number of rainy days and extreme events in the spring and in the magnitude of extreme fall rain.