Groundwater Cum Well Recharging Model

Though Kerala receives high rainfall of approximately 3000mm per annum, the temporal variations in its occurrence lead to acute water scarcity during the non-monsoon periods. Approximately 50% of the population in urban areas and 80% in rural areas still depend on open wells for their domestic water needs in Kerala. To augment the natural supply of groundwater, artificial recharge of groundwater has become an essential and proactive management strategy in the country (Government of India, 2017; Kerala State Planning Board, 2015).

Model for Groundwater and Well Recharge

The Thrissur District Administration launched the ‘Mazhapolima’ project in 2008, an artificial groundwater recharge scheme designed to recharge household dug wells directly with rainwater harvested from rooftops. By December 2012, approximately 8056 Mazhapolima units had been implemented in 58 Grama Panchayats with active participation from Grama Panchayats, private agencies, and beneficiaries. An investigation was conducted to assess the impact of the Mazhapolima project on the groundwater system in Thrissur District. Two sample areas (watersheds/GPs), very close to each other (with and without Mazhapolima), representing three physiographic regions of the district were selected for the study. One sample area in each physiographic region without the Mazhapolima project was selected as a control area (Centre for Water Resources Development and Management, 2013).

Impact Assessment

The analysis of hydrogeological data generated from the study area indicates that direct well recharge by rainfall harvested from rooftops is augmenting the groundwater reservoir. The increase in utilizable groundwater potential with Mazhapolima is estimated for the sample areas representing highland, midland, and lowland to be about 7.22, 14.08, and 43.35 million liters, respectively. The study also indicates that the impact of direct well recharge on the groundwater regime in the coastal and midland regions is very significant, whereas in the highland region it is marginal. This may be due to the relatively faster subsurface drainage in the moderate to steep topographical characteristics of the highland region (Kumar, 2014). About 347 respondents participated in the social survey, with 78% expressing the opinion that significant improvement in groundwater availability was observed in the coastal and midland areas. However, 68% opined that in the highland area, the improvement in groundwater availability was marginal. In the highland area, more than 50% of the respondents experience water scarcity during the summer months.

Challenges and Recommendations

About 68% of the respondents believe that proper maintenance of the system is crucial for its optimal functioning. The majority of respondents (85%) opined that there is a need for periodic maintenance of the recharge systems, usage of quality materials, and ensuring beneficiary participation in the implementation of the well recharge system for achieving better results. Physico-chemical analysis of water samples collected during post-monsoon, monsoon, and pre-monsoon seasons reveals a slight decrease in pH in well water samples collected from recharged areas. In the coastal region, it was found that the salinity level in water samples collected from recharged areas is relatively low compared to samples from non-recharged areas. High levels of bacteriological contamination were detected in the majority of water samples collected from the study area. This may be due to the close proximity of leach pits/septic tanks, etc. Lack of initial flushing may also lead to bacterial contamination in recharged wells. Bacterial contamination in recharged wells can be controlled to a large extent by the installation of a filter system and initial flushing. Periodic disinfection (chlorination) can control bacteriological contamination in well water to a large extent (National Institute of Hydrology, 2016).

Conclusion

The study revealed that direct well recharge by rainfall harvested from rooftops is augmenting the groundwater reservoir and improving water quality. However, proper attention must be given to the selection of the area, quality of materials, and installation of filters. Beneficiary participation must be ensured in the implementation and periodic maintenance to achieve better results and the sustainability of the Mazhapolima project. About 70% of households in the state still depend on groundwater through open wells to meet their domestic water demands. Hence, to enhance water availability in household wells, particularly during the summer months, the pilot project, Mazhapolima, implemented in Thrissur District, can be replicated in other districts through active beneficiary participation (Kerala State Planning Board, 2015).

References:
1. Centre for Water Resources Development and Management. (2013). Impact of Mazhapolima Project on the Groundwater Regime in Thrissur District Final Report.
2. Government of India. (2017). National Water Policy.
3. Kerala State Planning Board. (2015). Kerala Development Report.
4. Kumar, A. (2014). Groundwater Recharge Techniques in India. Journal of Water Resource Management.
5. National Institute of Hydrology. (2016). Guidelines for Drinking Water Quality.