Consolidate learning from the salinity ingress prevention measures undertake in the coastal area of Gujarat
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Summary The increasing salinity of land and water resources in the coastal areas of Saurashtra is a matter of grave concern for the Government in Gujarat. Salinization of groundwater causes socio-economic and environmental problems. Although already recognized by the Recharge Committee and the High-level Committees I and II in the early 1970s, still much work has to be done. However, the Salinity Ingress Prevention and Control along with some NGOs have constructed artificial recharge structures to arrest the salinity ingress. A joint effort by Deltares, IGRAC, Arcadis and the Ambuja Cement Foundation made it possible to perform a study for the salinity ingress problem. This study has got the objective to investigate the effectiveness of these artificial recharge structures to control the salinity ingress in the Kodinar region by developing a density driven groundwater solute transport model. Furthermore a qualitative analysis was carried out to investigate the salinization in the entire coastal area of Saurashtra by use of a simple groundwater balance approach. The model predicts for the reference scenario (stagnant situation) that the coastal region becomes fresher due to a positive groundwater balance based on the fact that only average years in terms of precipitation were used. As a consequence the seawater front does not seem to be moving towards inland although the model constraint that the cell dimensions are not adequate could also cause this. Incorporating dry years into the model could show other results and would level out the positive groundwater balance to zero. There is also up-coning in the upper areas where basalt is present. A low permeability combined with drainage cause this. Although the model results are not satisfactory for the reference case, the comparison between the various scenarios was very useful. It can be concluded that the use of artificial recharge structures along with drip irrigation are beneficial. The future outlook that the region becomes drier, the sea level rises and the fact that there is an increase in population have got strong negative implications for the salinity ingress problem. Assessment of the qualitative analysis of the coastal area of Saurashtra does not lead to valid conclusions as there was no correlation between the groundwater balance and the fraction saline area. This was caused by the fact that river fluxes could not be determined. However, the region of Kodinar and Talaja are gravely affected by salinity although the amount of storage of artificial recharge structures is very high. There is a lot of agricultural activity in these areas perhaps due to these artificial recharge structures. Probably in dry years the level of agricultural activity is maintained. This leads to a strong negative impact on the groundwater balance. It may therefore be concluded that the additional groundwater obtained from artificial recharge structures could act as a perverse incentive to use this water for additional agricultural activity making these areas very sensitive to salinization whenever a dry year occurs. In order to obtain reliable model results it is recommended that TDS-concentration and water table measurements should be measured in observation wells and more frequent to obtain an idea how the groundwater system works. More pump tests should be conducted to obtain more accurate hydraulic parameters of the soil. Additionally infiltration measurements and water heights of the river should be taken in order to determine a more reliable flux from checkdams, rivers and percolation tanks. It is recommended that water saving techniques like drip irrigation should be developed. Also additional artificial recharge structures are needed to control the salinity ingress problem. But most importantly, But most importantly, installation of a groundwater management approach program is recommended by integrating the various stakeholders, experts and the government into an organization which is responsible for the VII salinity ingress problem and the availability of fresh groundwater as a sustainable natural resource. Only by doing this the salinity ingress problem can be controlled efficiently.