1. Science View Importance of Groundwater and Surface-Subsurface Interactions Miguel A. Medina, Jr. Professor, Duke University miguel.medina@duke.edu First GEF Biennial International Waters Conference, October 14 – 18, 2000 Budapest, Hungary

2. Relation of streams, lakes, and wetlands to groundwater flow systems (Winter, Hydrogeology Journal, 1999) “Surface-water bodies are integral parts of groundwater flow systems. Groundwater interacts with surface water in nearly all landscapes, ranging from small streams, lakes, and wetlands in headwater areas to major river valleys and seacoasts.” “Hydrologic processes associated with the surface-water bodies themselves, such as seasonally high surface-water levels and evaporation and transpiration of groundwater from around the perimeter of surface-water bodies, are a major cause of the complex and seasonally dynamic groundwater flow fields associated with surface water.”

3. Complex Interactions

4. Overland - Channel Flow Component Net Rainfall Overland flow Stream - Aquifer Interactions Channel flow Free surface evaporation Infiltration

5. Saturated Flow Component Nearly horizontal flow Stream-Aquifer Interaction Impervious bed Unsaturated / saturated zone interaction Phreatic surface Pumping Reference datum z0z0 h H

6. Unsaturated Flow Component Infiltration Percolation / Capillary rise Phreatic surface Rainfall Unsaturated / saturated zone Interactions Soil Evaporation Root zone

7. evaporation phreatic surface leakage recharge root zone transpirationprecipitation / evaporation runoff Surface water body vadose zone Schematic of an example of surface-groundwater interactions. In this example, the surface water body is losing water to the groundwater zone.

8. Stream-Aquifer Systems Gaining stream Losing stream Losing stream induced by pumping well

9. Vital Elements for a Conjunctive Stream-Aquifer Model Element to calculate groundwater flow Element to calculate solute transport in aquifer Element to calculate stream flow Element to calculate solute transport in stream Element to account for stream-aquifer interaction

10. Accounting for Stream-Aquifer Interaction -- Lateral Exchange (Hyporheic Process) (After Harvey, et al., 1996)

11. Stream-groundwater exchange involving vertical and lateral interactions Steady state mass balance of water in the streambed: Mass balance of solute in the streambed: (After Battin, 1999)

12. Conjunctive Use Water Supply Schemes Take advantage of the most favorable characteristics of surface and subsurface storage of water Enhance long-term availability through use of large storage volume in most aquifers to store surplus surface water During droughts, when surface supplies dwindle, recover stored aquifer water by pumping (ASR – Aquifer Storage Recovery) Low quality surface water may be filtered by porous media percolation

13. Transport of water from one storage facility to another – unique to conjunctive use Stream channels, pipelines, tunnels, open channels Storage reservoirs (high evaporative loss) Artificial recharge – permeable beds of rivers, surface spreading basins (losses due to evaporation, absorption), injection wells (pre-treatment required for high quality)

14. Common Arab-Israeli Surface and Groundwater Resources (Kliot and Shmueli, 1998) Lebanon, Syria, Israel, Jordan and the Palestinian Authority share the Jordan River and its tributary, the Yarmuk The Upper Jordan (Lake Kinneret) has three sources: the Hasbani (Lebanon), the Banias (since 1967 controlled by Israel, and the Dan (Israel) Syria, Israel and Lebanon share the Upper Jordan Syria, Israel, Jordan and Palestinians share the Lower Jordan Israel and Palestinians share groundwater

15. Over-Utilization of Jordan-Yarmuk system (Kliot and Shmueli, 1998) The Yarmuk River – the most important tributary of the Jordan River, has a discharge of 400-500 Mm 3 /year. Over-utilization of the Jordan-Yarmuk system has resulted in a decline of the total discharge of the Jordan into the Dead Sea to 250-300 Mm 3 /year, accelerating the decline of the Dead Sea. Most of this discharge is actually irrigation return flow, inter-catchment runoff, saline spring discharges and sewage dumped by Israel to the Lower Jordan.

16. Israeli-Palestinian Shared Groundwater Resources (Kliot and Shmueli, 1998) Mountain Aquifer – 3 sub-aquifer systems: Western (300- 335 Mm 3 /year); the Northeastern (130-150 Mm 3 /year); the Eastern (150-250 Mm 3 /year). Total annual recharge is about 680 Mm 3 /year. Israel uses about 480 Mm 3 /year and the estimate for the Palestinians is 110-180 Mm 3 /year. Coastal Aquifer (in the Gaza Strip) yields 60 Mm 3 /year but is overexploited by 30-50 Mm 3 /year, with total pumping of 90-110 Mm 3 /year. Issue of water quality perceived as important as water quantity in peace treaties and agreements.

17. Joint Management Structures for Cross-Boundary Aquifers (Feitelson and Haddad, 1998) Need is likely to become acute in near future, as reliance on aquifers grows, and water stress increases Yet, there is scant experience in management of cross- boundary GW resources Gradual simple positive steps, such as joint monitoring and data sharing, should be taken first. At the same time, these steps should be part of a more comprehensive institutional development path.

18. Transboundary Freshwater Dispute Database (http://terra.geo.orst.edu/users/tfdd) 150 water-related treaties, 39 U.S. interstate compacts, catalogued by basin, countries, date signed, conflict resolution mechanisms, etc. (Wolf, 1999) Digital map of 261 international watersheds Full text of each treaty and compact

19. Water Conflict Chronology Pacific Institute for Studies in Development, Environment, and Security (2000) http://www.worldwater.org/conflictIntro.htm Covers water conflicts from 1503-2000