A hydrologic balance approach to saline seep remediation design

Concern about saline seeps is increasing in the dryland production regions of Kansas and the North American Great Plains. To reclaim salt-affected see p areas, site hydrologic factors must be modified to reduce seep recharge. A simple method is needed to help design effective remediation treatments. A hydrologic balance model, POTYLDR (Potential Yield Model, Revised), was m odified and used to estimate the water balance in a saline seep recharge ar ea and to estimate the effectiveness of various acreages of alfalfa treatme nts in reducing seep recharge. This model uses readily available data, such as daily rainfall and temperature, NRCS runoff curve numbers, NRCS soil ir rigation classes, Penman evapotranspiration parameters and Blaney-Criddle c rop coefficients, to determine runoff evapotranspiration, soil moisture, an d percolation from the root zone. According to the assumed seep mechanism, deep percolation from the local recharge area was used to estimate seep rec harge. Various percentages of the seep recharge area were shifted from the current wheat cropping to alfalfa to determine the reductions in total rech arge and number of months contributing to recharge. A 50% reduction in tota l recharge required 14 to 32% alfalfa acreage depending upon site-specific factors of five targeted fields. A given alfalfa acreage reduced total rech arge volume more effectively than it reduced the number of months contribut ing to recharge. The major limitation in application of these results is se lection of the percentage seepage reduction needed to provide seep control. The modeling approach provides an important indication of a system's respo nsiveness to changes in vegetation and quantifies this response in a May th at is useful for designing bioremediation treatments that require control o f seepage or shallow groundwater recharge.