Identifying cause of declining flows in the Republican River

The Republican River, shared by three states, Colorado, Nebraska, and Kansa s, has yielded depleted streamflow at the Nebraska-Kansas border for about 20 years when compared to values preceding 1970. Based on model results est imating the average annual water balance of the basin, it is concluded that the observed decline in runoff cannot be explained by changes in climatic variables over the area; rather, it is the result of the combined effects o f the following human activities: crop irrigation, change in vegetative cov er, water conservation practices, and construction of reservoirs and artifi cial ponds in the basin. These human-induced changes have one property in c ommon: they all increase the amount of water being evaporated over the basi n, thereby reducing the amount of water available to runoff.