USING NATIONAL DATASETS TO DETECT STREAMFLOW DEPLETION IN THE MIDDLE ARKANSAS WATERSHED, KANSAS

Streamflow depletion, which is a reduction in streamflow caused by groundwater pumping, is important to agriculture and society. Streamflow depletion is a hidden process that is challenging to measure directly and is often obscured by other process such as surface-water diversions and climate change, so metrics are often used to quantify and explain depletion. We sought to identify hydrologic signatures that can help detect, and relate physical processes to, streamflow depletion. We test these signatures in the Middle Arkansas River watershed, which has rich national and local data sets and known impacted streams. In these areas, nationally there are data-dense gage stations from 1963 – 2021 and long-term gages stations with more than 100 years of data. Locally there are detailed histories of water use and groundwater levels that can be used to supplement the national data sets. The temporal trends identified among high-density data show how the river changes spatially across different climate regimes, over aquifers, and through dams, diversions, and areas of extensive groundwater use. While upstream areas with limited water-use infrastructure have increased or neutral baseflow trends, areas with increased water-use infrastructure demonstrate decreased baseflow trends. Long-term trends show how the river responds to climate variations pre- and post- diversion and water-use practices. Using this approach, we have been able to tell the story of the Arkansas River quantitatively and qualitatively as it traverses the state of Kansas. Our findings suggest that, as long as confounding factors are accounted for, hydrologic signatures based on national datasets can be used to identify when and where streamflow depletion has occurred.