Flow processes in a rangeland catchment in California

Emerging hydrology-related issues in California grasslands have directed at tention towards the need to understand subsurface water flow within a compl ex, dynamic system. Tensiometers and neutron probes evaluated the subsurfac e hydrology of a rangeland catchment. Hydrological processes within the cat chment varied both in space and time. Spatial variability was evident along the vertical profile and between the catchment slopes. Temporal variabilit y in processes coincided with the seasons (i.e., wet winter, dry summer, an d spring). From a water-balance equation developed for the catchment, we de termined that there was significant variability both spatial and temporal i n the amount of soil moisture lost to evapotranspiration and deep seepage. During the 16 month monitoring period there was a total of 50 cm of rainfal l that fell in the catchment of which 9-55 cm was lost to evaporation and 3 7-79 cm to deep seepage. A simple deduction of the losses (evaporation and deep seepage) from the input (rainfall) shows that all monitored locations had a substantial decrease in the amount of water that was stored in the so il profile.