FACTORS AFFECTING GROUNDWATER RECHARGE FOLLOWING CLEARING IN THE SOUTH WESTERN MURRAY BASIN

Data from 18 field studies in the south western Murray Basin (Australia) and a simple water balance model were used to study the importance of factors which affect diffuse recharge in that area. Generally as the texture of the soil became heavier the recharge decreased. Under cropped land as the clay content in the top 2 m of the soil profile increased from 0 to 20%, recharge decreased by one order of magnitude (from about 30 to about 3 mm year-1, for a mean annual rainfall of 310-380 mm). As mean annual rainfall increased the mean annual recharge also increased. Sites with an average clay content of about 10% in the top 2 m and a mean annual rainfall of 270 mm had an estimated recharge of about half that of sites with a mean annual rainfall of 310-380 mm. Data from land which was grazed but not cropped showed similar relationships. However, the data set did not allow a detailed analysis of the effect of land use on recharge.