Hydrology & Climatology (including Geohydrology) Louisiana Department of Environmental Quality 2010 Envirothon Training

The Hydrologic Cycle Consists of inflows, outflows, and storage

What is Groundwater? Any water beneath the ground surface. Groundwater is stored in aquifers. What is an Aquifer? A water-bearing stratum (or layer) of sand and/or gravel that yields significant quantities of water to wells. A water-bearing stratum (or layer) of sand and/or gravel that yields significant quantities of water to wells. Groundwater 101

Vadose Zone – water partially fills pore spaces Saturated Zone - all pores are filled; water table is upper boundary

Porosity & Permeability Porosity is the percentage of a material occupied by void space or “pores.” Permeability is a measure of the interconnectedness of the pore space allowing the material to transmit water. The rate at which a material transmits water depends on its total porosity and the size of the interconnections between voids (permeability). Aquifers – gravel, sand Aquitards (impede flow) - clay

Aquifers

Surface Extent of Louisiana’s Aquifers and Aquifer Systems

**Aquifers in Southeastern Louisiana collectively called Southern Hills Aquifer System **

Cross Section Example - -Identify recharge areas - -Where are the aquifers confined and unconfined?

Drawdown Understanding drawdown/cone of depression is important to: Ensure continuous supply of water (avoid “dry wells”) Management of overlying land area (vulnerability) Identify source of ground water (water once discharging to a stream may now be pulled into well)

Impact of Pumping on Natural Ground Water Flow Strategic Placement of wells Design of appropriate pumping rates & frequencies Manipulate ground water flow

Groundwater - Surface Water Interaction Gaining Stream - Altitude of water table higher than altitude of stream-water surface -- groundwater discharges to stream Losing Stream - Altitude of water table lower than altitude of stream-water surface -- surface water recharges groundwater

Groundwater Recharge & Discharge Recharge – - Infiltration – - Losing Streams – - Artificial Discharge – - Springs – - Gaining Streams – - Pumping wells – - Flowing artesian wells

Effects of Groundwater Withdrawal on Surface Water Groundwater discharges to stream under natural conditions Pumping well at rate of Q1 intercepts some of groundwater that would have discharged to stream Pumping well at rate of Q2 intercepts additional water and draws water from stream (Q2 > Q1) **Stream quality affects groundwater quality

Impacts of Global Warming Changes in groundwater recharge resulting from changes in precipitation and temperature More severe and longer lasting droughts which could lead to overdraft and saltwater intrusion Possible increased demand Surficial aquifers most sensitive Affects energy use and production