INFLUENCES OF LAND USE AND WETLAND CHARACTERISTICS ON WATER LOSS RATES AND HYDROPERIODS OF PLAYAS IN THE SOUTHERN HIGH PLAINS, USA

摘要

More than 25,000 playa wetlands are embedded in the Southern High Plains (SHP), USA. The SHP is one of the most intensively cultivated areas in the world and, as a result, the function of playas has been altered by deposition of eroded sediments. We monitored water levels in 33 playas in summer 2003 to examine the influence of land use (cropland vs. native grassland) and playa characteristics (playa area, watershed size, starting water level, volume loss, sediment depth, percent playa vegetation cover, and soil texture zone) on water loss rate and hydroperiod (consecutive days a playa held measurable surface water). Multiple regression models (selected using Akaike's Information Criterion) indicated that land use, percent playa vegetation cover, and soil texture zone were important factors explaining water loss rate while starting water level and land use were important in explaining hydroperiod. Playas with cropland watersheds have lost their hydric soil-defined volume due to sedimentation, which results in an increase in water surface area and evaporation, and possibly infiltration, thus shortening hydroperiod. Hydroperiod was not related to playa area. Based on hydroperiod, small playas should receive the same conservation consideration as larger playas. Future research should examine transpiration rates in playas within grassland and cropland landscapes.