Reservoir Water Supply Management: Potential Impacts of Precipitation and Discharge Pattern on Reservoir Sedimentation
Vahid Rahmani, Jerry deNoyelles, Don Huggins, Jude Kastens, and Edward Martinko
Providing reliable water supply is one of the greatest concerns in water management systems, particularly in the areas that have highly variable weather and extended drought periods such as central and southern Great Plains. Streams, lakes, reservoirs and groundwater resources are the main sources for water supply in the central and southern Great Plains, including Kansas. Aside from groundwater in the low populated counties of western Kansas, the 24 federally-operated reservoirs of central and eastern Kansas are the most important drinking water sources for the state. Water demands has been growing due to population increase and more agricultural needs, less reservoir storage capacities due to sedimentation, and a highly variable climate in the state. Understanding precipitation and discharge patterns is necessary in planning/operating water management systems sustainably, as conditions vary and/or change. In this study the nonparametric Man-Kendall method was used to analyze precipitation and discharge trends for the 24-federal reservoirs. Precipitation indicated a spatial pattern from a semi-arid condition in the west (500 mm/year) to a humid continental condition in the east (950 mm/year). Trend analysis demonstrates a positive slope for the total annual precipitation for a majority (14 out of 24) of the reservoir watersheds with greater slopes in the eastern Kansas. On the other hand, streamflow showed decreasing trends in a majority (21 out of 24) of the reservoirs. The upward precipitation and downward streamflow trends impact the available water in reservoirs and infilling sedimentation rates. The output of this study is useful for reservoir water and sediment managers, policy and decision makers, and other Kansas stakeholders such as farmers.