Inflow to the Highland Lakes has substantially decreased from 1942–2013, likely due to increased evapotranspiration from the proliferation of 19 major upstream reservoirs and about 69,500 minor reservoirs and water bodies. Increased evapotranspiration from land surfaces and stream channels also probably represent major causes for inflow reduction. Eight climatic indices were evaluated with respect to correlations with inflow volumes to the lakes. A combination of the indices for the Atlantic Multidecadal Oscillation and Oceanic Niño Index (Niño 3.4 region) was found to be, up to three months in advance, a fair indicator for the wettest three-month inflow periods, and a good indicator, up to nine months in advance, of the driest three-month inflow periods. The single best index indicator of dry periods is the Pacific Decadal Oscillation—a good indicator of the driest three-month periods up to a year in advance.
© 2020 Raymond M. Slade, Jr.Download PDF