Spatial characteristics of playa lakes in castro County, Texas

The study area contained 666 ephemeral playa lakes, located in surficial depressions with fine textured Randall clay soil, and 2 transecting and 2 protruding draws (ephemeral waterways). Soil Conservation Service County Soil Survey and U.S. Geological Survey data for the size, elevation and depressional depth of each lake were analysed using 2 standard statistical programs, a geostatistical program and several BASIC programs. Playa lake size was predominantly 3.2-28.3 ha with an average drainage basin of 382 ha. Large lakes tended to occur in the east and deeper lakes in the southwest. Analysis of the individual influence of each draw on playa distribution using linear modelling showed no clear relationships although playa orientation in the immediate draw area appeared (visually) to be highly related to draw orientation. Correlation coefficients of angular directional relationships for size, depth and elevation of all playas indicated that the strongest linear spatial distribution occurred along a west northwest-east southeast axis for the county as a whole.