nawqa_precip is a line and polygon coverage of the precipitation values in the Cook Inlet Basin National Water-Quality Assessment (NAWQA) study area in southcentral Alaska. This coverage was created using a statewide map showing lines of equal annual precipitation prepared for a flood frequency study (Jones, S.H., and Fahl, C.B., 1994). Values for each polygon bounded by lines of equal annual precipitation were generally determined by averaging the precipitation values of the bounding lines.
The purpose of the coverage is to provide information on the amount of precipitation which occurs within the Cook Inlet watershed. This coverage, along with other GIS coverages, will be used to help locate water-quality sampling sites for the Cook Inlet NAWQA study. The coverage was created using a statewide map (1:2,500,000) showing lines of equal annual precipitation The map was developed in 1993 as part of a flood frequency study of Alaska's streams and rivers. Values of precipitation for the various polygons were determined by interpolation between the isolines. Boundaries of this coverage were drainage-basin divides for areas draining into Cook Inlet using a coverage containing hydrologic unit codes (HUC).
