Proposal to study the effect of Global warming on ground water at Al-Batinah cost

1. 1. Rationale Oman is country lying in the arid/semi arid region with a mean annual rainfall of 50 mm/year over coastal plains and desert areas, and around 350 mm/year on mountains area. With very limited water resources groundwater contributes to drinking water sources in the country providing almost 27% of the total drinking water consumed in the country with the other 73% being provided from seawater desalination plants (The Annual Book of Housing & Water Statistics) Such a proportion is putting a lot of pressure on the groundwater already, and with the increasing demand on water it is of vital importance for decision makers to know the amount of groundwater available for domestic, industrial and agricultural uses in order to continue with the development plans the country is going through. Global warming is a phenomenon that is already affecting the hydrological cycle in some areas of the world with many countries facing more frequent droughts than in the past whilst rainfall and flooding have intensified in some areas (Dragoni. W. and Shukhija, B. S.). Many studies outlined the main points of impact of global warming on the hydrological cycle, but very little has been done to forecast the amount of groundwater recharge based on different global warming scenarios. This study aims at evaluating the amount of groundwater expected to be available with the different climate change scenarios in Al Batinah coast which is the most populated area in the country. Sea water intrusion affected many areas across the coast line in that area due to over abstraction of groundwater during the 70’s and 80’s of the last century for agriculture. Hence, the water quality in the area is seeing a decline and the situation could be worsened with the expected sea water level rise due to global warming which might result in the seawater/freshwater interface being pushed further inland. 2. Objectives To asses the effect of global warming on groundwater resources in the coastal areas of Oman (Al Batainah region) in terms of availability and quality for the coming 10-20 years 3. Theory Water resources are central to any study on climate change. In areas that rely heavily on groundwater, for agriculture, domestic or industrial use, it is important that the potential impacts of climate change be assessed so that adaptation measures are taken. Climate change will directly affect groundwater recharge, timing of recharge events storage in aquifers, the quality of groundwater and the freshwater/seawater interface (Dragoni. W. and Shukhija, B. S.). These impacts are of paramount importance for many reasons, not the least that groundwater is and will be the main solution to water scarcity during droughts in arid and semi arid areas. It is imperative therefore to establish rational management and conservation plan. It is expected that changes in temperature and precipitation will alter groundwater recharge to aquifers, causing shifts in water table levels in unconfined aquifers as a first response to climate trends (Scibek j. et al, 2008) Climate and the hydrogeologic environment are the joint control of groundwater recharge discharge and storage. Amounts and pathways of aquifer recharge differ greatly from humid to arid climatic regions, with consequent influences on groundwater storage and discharge. Temporal changes in climate are reflected in groundwater fluxes, albeit with dampening of high frequency variations. Groundwater fluxes are a component of the surface water balance, which tightly coupled to atmospheric processes and thus to climate. Because groundwater is one of the major reservoirs in the hydrosphere, charges in volume would also be reflected ultimately by changes in sea level (Committee on Hydrologic Science). 3.1. Impact of climate change on groundwater recharge and discharge Climate variations and change will affect groundwater systems primarily by changing the rates and distributions of recharge of water to aquifers, the discharge of water from aquifers, and the removal of groundwater from aquifers by plants and human activities as near-surface water availability and energy inputs change. At long term scales, the salinity conditions and discharge at the freshwater/salt water interface of costal aquifers may (or may not) be in equilibrium with modern ocean levels and conditions, and a better understanding these conditions and the underlying causes would enhance the understanding of climate-scale variability of coastal aquifers. Therefore, a better understanding of groundwater recharge, discharge and demands vary with climatic fluctuations and change will be the first and most essential requirement for addressing the boarder question of climatic impacts on both the surface and subsurface hydrology (groundwater fluxes across interfaces, Committee on Hydrologic Science, National Research Council). Groundwater recharge is determined to a large extent as an imbalance at the land surface between precipitation and evaporative demand; the latter depends primarily on the surface radiation balance and also on atmospheric temperature, humidity and wind speed. When precipitation exceeds evaporative demand by an amount sufficient to replenish soil-water storage, any further excess flows deeper into the ground, arriving at the water table as recharge. Groundwater therefore responds to temporal variations in climate. Because of the relatively slow response of many groundwater systems to changes in forcing, however, they tend to reflect much more the low frequency climate signal than the high frequency weather fluctuations (Committee on Hydrologic Science). This tendency contributes to the value of groundwater climate changes and the resultant changes in groundwater characteristics. Given the relatively long response times of groundwater systems, it is the climatic variations at longer time scales that most strongly influence changes in groundwater recharge. At shorter time scales, groundwater recharge will be affected by the short term variations of precipitation and evapotranspiration (decades to centuries), caused by either long term variability or anthropogenic recharge and availability. 3.2. Climate change and groundwater quality The climate is expected not only to affect input (recharge) and output (discharge) but also to influence the quality of the groundwater. Climate change can directly affect water quality; for example water recharge during an arid period may have higher concentration of salts and TDS while during wet period the converse may occur. Climate change can alter groundwater quality also indirectly by increasing the level of evapotranspiration due to surface temperature increase or by the rise in seawater level in costal areas which could result in seawater intrusion in areas of fresh groundwater. Method A good knowledge of the geology and hydrogeology of the study system is an essential prerequisite to investigating the impact of climate change. The study of groundwater resources should be based on a reliable, continuous and dense data-base of hydrometeorological data and soil moisture, covering a long time interval. These data should be coupled with large spatially distributed quantitative information such as hydraulic conductivity and porosity. A high quality network of data collection must be established; this will help to evaluate the present situation and also follow the evolution process and therefore validate the knowledge gained through time. Reference: Dragoni. W and Shukhija, B. S.in: Climate change and groundwater , Dragoni, W. and Sukhija B. S. ed. Proceeding to the XXXII International Geological Congress (August 2004, Flrence, Italy) Scibek j. et al, 2008 Proceeding to the XXXII International Geological Congress (August 2004, Flrence, Italy) groundwater fluxes across interfaces, Committee on Hydrologic Science, National Research Council The Annual Book of Housing & Water Statistics, Ministry of Housing, Electricity &Water, 2006