ABSTRACT:

Due to the on-going decline of the alluvial aquifer and the lack of available excess surface water for irrigation diversions in the Cache River critical groundwater area (CRCGA), future resource allocation decisions made in the region will benefit from specific, detailed assessments conducted at the sub-watershed level. Assessments of available water and land resources can be used to identify and prioritize potential sites for conjunctive use projects such as on-farm irrigation reservoirs and in-stream weirs. These can then be integrated with agronomic-irrigation practices to devise different management practice scenarios with the ultimate goal of reducing groundwater withdrawals. To this end, multiple publicly-available geo-referenced spatial data sets for the region were analyzed, including aerial and satellite imagery in visible and near-infrared bands, annual crop type and yields, soils, elevation, along with stream reaches from the National Hydrography Dataset. With this data, possible locations for weirs, reservoirs, and conservation practices were identified. The targeted locations for weirs were related to straight length and slope of a stream reach, and those for reservoirs and conservation set-asides could be related to areas of low productivity and/ or low elevation, poorly draining soils, etc. An interesting result of the assessment that highlights the need for such work was that the subwatersheds over the center of the aquifer cone of depression were also in the headwaters of the L’Anguille River. Streams in these subwatersheds may be too small to support weirs, and thus farmers in the area would have to rely solely on irrigation conservation measures and on-farm storage reservoirs to capture rainfall and field runoff to reduce groundwater withdrawals.

Presentation at 2018 AWRA Spring Specialty Conference: Geographic Information Systems (GIS) and Water Resources X, Orlando, Florida, April 23-25, http://awra.org/meetings/Orlando2018/