Climate change is one of the many factors responsible for Kerala’s depleting groundwater levels, but to combat it, Anand Jakarayas, Development Associate (Water), MS Swaminathan Research Foundation, explains how open well recharge systems can help Kerala overcome the water crisis. helping. The open well recharge system is superior to other methods, as experiments have shown that scraping off the top sediment layer and 15 cm of topsoil can restore up to 68.3 percent of the initial infiltration capacity. Sometimes aquifers contain clay lenses, if the recharge water has high total dissolved solids (TDS) or high sodium concentration, the clay lens may move through the thick layers of the aquifer with groundwater, pumped from wells. The water used will be dirty.
File Photo : Akshay Deshmane
In terms of cost and effectiveness, the cost seems to be low compared to artificial open well recharge systems and other water recharge systems. Methods based on surface infiltration have relatively low construction costs and are easy to operate and maintain. However, surface infiltration systems are not always suitable. This is not possible where permeable surface soil is not available, land is very expensive or there is poor-quality water on top of aquifers.
Direct subsurface recharge methods reach deeper aquifers and require less space than direct surface recharge. However, they are expensive to manufacture and maintain. Recharge wells, commonly called injection wells, are commonly used to replenish groundwater. This is done when the aquifer is deep and usually separated from the land surface by materials of low permeability.
In areas where the base flow of streams is supported by groundwater, adding storage for recharge and groundwater flow can result in higher sustained flows during low flows or drought conditions. The flow of the springs can be maintained at a high level even during summer through groundwater that would result from artificial recharge. On the other hand, surface reservoirs whose water quality has been reduced by low-quality water released from the aquifer can harm the ecology of the surface reservoir.
Cultural factors should also be taken into account when finalizing the type of recharge structure method and the location of the structure. Land availability, land use in surrounding areas, public attitudes, and legal requirements all contribute significantly to the successful implementation of an artificial recharge system. For example, in urban areas, injection wells with controlled water supply are preferred.
There are many benefits of open-well recharge system. It increases the availability of groundwater and groundwater table and is effective in all ecosystems across Kerala. Moreover, this technology helps in improving the quantity as well as quality of water in aquifers in rural areas.
Broadly speaking, the biggest reason for the continuous depleting groundwater level is the increase in the number of borewells. Salinity increases especially during the summer season as the groundwater level drops below mean sea level, facilitating lateral or vertical movement of salt water. As a result of this action, this salty water can enter the groundwater reservoirs. Similarly, the rivers of Kerala often face salinity intrusion in their lower reaches during the summer months when the flow of fresh water is reduced. The monsoon usually recharges the groundwater table sufficiently, leading to a low concentration of saltwater in the aquifers.
Kerala has a distinctive coastal aquifer system which is prone to saltwater intrusion into groundwater sources including wells. A rise in the sea level or a fall in the groundwater level or a change in tide or breaking of aquifers, etc., can lead to saltwater entering the wells. Around 50 wells in Poovar in Kerala alone have been affected by saltwater encroachment. Due to salty water, some people in rural areas are forced to resort to water pipelines, which are more expensive for them. Destruction of freshwater lakes and conversion of wetlands contribute to the decline in groundwater levels. The rising sea level due to global climate change is one of the reasons directly affecting this problem.
In Kerala, groundwater salinity is due to leaching of salts from aquifer material, not seawater intrusion. This is due to the fact that groundwater aquifers are mostly confined in Kerala which restrict direct seawater intrusion, and this is the reason why no seawater ingress into coastal waterways due to over-extraction has been reported from the Kerala coast. Is. However, salinity is observed in shallow wells that are close to backwaters, lagoons, lakes and tidal rivers. The coastal wells located at Kadalundi and Kottakkal are partly influenced by lagoon and partly by seawater as they have sea on one side and lagoon/backwater on the other. This problem is also found in places like Vadakara, Thiruvangur Beypore, Kozhikode beach, etc.
Photo courtesy: Deccan Herald
The presence of salt water in wells is an indicator of groundwater quality. Sodium chloride (AcCl) or common salt is the major salt found in groundwater, followed by magnesium chloride (MgCl). Some groundwater also enters surface water bodies such as canals, lakes, or streams, thereby altering the hydrology of surface water. The brackish water cannot be used for paddy cultivation which is a major economic activity of Kerala. The intrusion of salinity into groundwater mainly affects the supply for agricultural, industrial and domestic use. Due to the fall in the groundwater level, more and more borewells have to be dug, as a result of which the efficiency of the pumps is also decreasing. In addition, poor households in rural areas spend about two hours a day fetching water.
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Author: Anil Ashwani Sharma
Publish On: May 13, 2022.