Watershed Water Resource Assessments in the Cache River Critical Groundwater Area for Future Targeting of Conjunctive-Use and Conservation Projects

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/

鉴于沙质含水层持续衰退以及Cache河关键地下水区域（CRCGA）缺乏可供灌溉改道的多余地表水资源，该区域未来资源分配决策将受益于在子流域层面的具体详细评估。对现有水资源和土地资源的评估可用于识别和优先考虑联合使用项目如农田灌溉水库和河中堰坝等潜在地点。随后，这些项目可与农学灌溉实践相结合，以制定不同的管理实践场景，最终目标为减少地下水开采。为此，对多个公开可用的区域地理参照空间数据集进行了分析，包括可见光和近红外波段的航空和卫星影像、年度作物类型和产量、土壤、高程，以及国家水文数据集中的河流段落。利用这些数据，确定了堰坝、水库和保育措施的潜在位置。评估的一个有趣结果是，突出了此类工作的必要性，即含水层降落漏斗中心的子流域也位于L’Anguille河的上游。这些子流域中的河流可能过于狭窄，无法支持堰坝，因此该地区的农民将不得不完全依赖灌溉保育措施和农田储水水库来捕捉降雨和地表径流，以减少地下水开采。

在2018年AWRA春季专题会议上的展示：地理信息系统（GIS）与水资源X，佛罗里达州奥兰多，4月23日至25日，http://awra.org/meetings/Orlando2018/