Ecohydrology

Irrigation percolation can be an important source of shallow aquifer replenishment in arid regions of the southwestern United States.  Aquifer recharge derived from irrigation percolation can be more significant in fluvial valleys overlying shallow aquifers where highly permeable soils allow rapid water infiltration and aquifer replenishment. We used data from various irrigation experiments and piezometric level data to assess irrigation percolation effects on recharge of a shallow aquifer in an agricultural valley of northern New Mexico. The water balance method (WBM) and the water table fluctuation method (WTFM) were used for estimating aquifer recharge at the field scale (< 1 ha) and the WTFM was used for determining recharge at the entire valley scale (40 km2). Also, the temporal and spatial distribution of aquifer response to irrigation percolation and canal seepage inputs was characterized. Results showed that for separate irrigation events at the field scale, aquifer recharge values ranged from 0 to 369 mm when using the WBM and from 0 to 230 mm when using the WTFM.  For the cumulative irrigation season at the valley scale, recharge ranged from 1044 to 1350 mm yr-1. A relatively rapid water table response with sharp water table rises and declines was observed in all but dryland location wells in response to canal seepage and irrigation percolation inputs. Results of this study add to the understanding of the mechanisms of shallow aquifer recharge and the interactions between surface water and groundwater in a floodplain agricultural valley of northern New Mexico.