Questions regarding Ogallala Aquifer groundwater availability

1. Questions regarding Ogallala Aquifer groundwater availability Do we really have any idea what our groundwater reserves are? Robert E. DeOtte Jr., Ph.D., PE., PG. Professor of Civil & Environmental Engineering

2. Mass Balance, Groundwater Modeling, and Geographic Information Systems to Improve Estimates of Available Reserves in the Ogallala Aquifer Objective: To apply concepts of conservation of mass using estimates of cropland irrigated by crop type and expected irrigation water added. Collaboration between WTAMU & TTU

3. Project Planning- Front End Technology Transfer - • HPUWD • HCUWCD • PGCD • Texas AgriLife Research • USDA-ARS Bushland • Daniel B. Stephens • WTAMU • TTU • TWDB • NPGCD What do we know about the water levels in the Ogallala Aquifer? What do we know about the reserves in the aquifer? Approach: Planning workshop at West Texas A&M University.

4. Determining Groundwater Reserves Texas Tech University Center for Geospatial Technology

5. Groundwater Districts • Base of Aquifer Data (Red Bed) • Monitoring wells • Most are or were pumped wells monitored in the off-season • North Plains Groundwater Conservation District • 425 monitor wells • 41 district owned • 22 constant recorded equipped • Flow meters

6. GAMs Modeling • Texas Water Development Board • Contractors • MODFLOW • Multilayer finite difference model • Calibrate • Known water levels • Data reported by GWCD to TWDB • Historic patterns • No Mass Balance

7. Darcy’s Law – Modeling Issues Homogeneity and isotropy of K Spatial variability of SS How much variation is there within a county? How sensitive are predictions to this? How do we know ?

8. Estimated water used for irrigation Deaf Smith County

9. Mass Balance Approaches • What goes in comes out • Measure flows from wells • Direct – meters • Indirect – ET and agronomic • Measure flows from springs and seeps • Measure recharge • Measure flux across model boundaries

11. Questions & Concerns ?