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Using Ecologically Relevant Hydrologic Indices to Examine Temporal Changes in Unregulated Streams in Kansas

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2010 Pittsburgh, Pennsylvania, June 20 - June 23, 2010  1009056.(doi:10.13031/2013.29794)
Authors:   Jonathan P Aguilar, James K Koelliker, David G Chandler
Keywords:   hydrologic indices, Kansas, aquatic ecology, trend analysis, Great Plains, streamflow.

Irrigation water demand in the Great Plains region is lowering groundwater levels, reducing base flow and dewatering vulnerable streams. In western Kansas, groundwater has ceased to supply dependable baseflow to previously perennial streams. The change in baseflow has altered both the natural flow regime of streams and the level of in stream connectivity among pools at low flow. Previous studies have shown that changes occurring in streams have adverse impacts on freshwater ecosystem and fish species distribution. The objective of this study was to document stream flow regime changes for unregulated streams in four geographically distinct regions across Kansas using 60 or more years of daily discharge data. The analysis focused on spatial differences and temporal changes in hydrologic indices relevant to the lotic ecosystem for fourteen unregulated streams. Log Pearson III method was used for computing flow probabilities. The Mann-Kendall test in conjunction with Sens slope estimator was used for trend analysis. Indicators of Hydrologic Alterations software was used to generate hydrologic indices. Results show a substantial difference in streamflow characteristics between western and eastern regions. Temporally variable indices include median, zero and 1 cfs flow, and timing of low flow. Most streams in western Kansas now have longer and more frequent dry periods. Moreover, the timing of these dry periods could adversely impact essential ecological services and functions. Results of this study are intended to guide decision makers, watershed stakeholders, and environmental conservation advocates in addressing problems and concerns related to stream and river management.

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