SUSTAINABLE GROUNDWATER USE IN AN UNCONFINED ALLUVIAL TERRACE

Alluvial terraces often contain easily accessible shallow groundwater; however, they are commonly limited in areal extent and contain thin saturated sections within heterogeneous sediments. These characteristics make them difficult to use efficiently and sustainably. This study assesses a terrace aquifer used by a 42-acre farm near Waco, Texas, to make recommendations for sustainable groundwater management.

The farm is owned and operated by World Hunger Relief Incorporated (WHRI) located in McLennan County northeast of downtown Waco. WHRI is committed to alleviating food insecurity and malnutrition through sustainable agriculture. The main irrigation source for the farm is groundwater in an unconfined alluvial terrace deposit composed of clay, silt, sand, and gravel that overlies marine shale bedrock. The terrace encompasses the southern portion of the property and the northern portion is a bedrock outcrop.

Core samples were obtained using a Geoprobe 6620DT (Geoprobe, Salina, KS) to describe and quantify the alluvial sediment. Piezometers and a rain gauge were installed on site to monitor water levels and estimate saturated volume. Water levels, rainfall events, and chemical field parameters were analyzed to estimate recharge and assess water quality. Analysis of core samples and piezometer data revealed a saturation anomaly. The cause and impact of this anomaly are yet to be determined.

Results from this study will be incorporated into a 5-year master plan for the WHRI to aid in the sustainable management of groundwater usage for the site and will provide a foundation for future studies regarding alluvial terrace groundwater systems.