Abstract
The managed aquifer recharge (MAR) of excess monsoonal runoff to mitigate downstream flooding and enhance groundwater storage has received limited attention across the Indo-Gangetic Plain of the Indian subcontinent. Here, we assess the performance of a pilot MAR trial carried out in the Ramganga basin in India. The pilot consisted of a battery of 10 recharge wells, each 24 to 30 m deep, installed in a formerly unused village pond situated adjacent to an irrigation canal that provided river water during the monsoon season. Over three years of pilot testing, volumes ranging from 26,000 to 62,000 m3 were recharged each year over durations ranging from 62 to 85 days. These volumes are equivalent to 1.3–3.6% of the total recharge in the village, and would be sufficient to irrigate 8 to 18 hectares of rabi season crop. High inter-year variation in performance was observed, with yearly average recharge rates ranging from 430 to 775 m3 day−1 (164–295 mm day−1) and overall average recharge rates of 580 m3 day−1 (221 mm day−1). High intra-year variation was also observed, with recharge rates at the end of recharge period reducing by 72%, 88% and 96% in 2016, 2017 and 2018 respectively, relative to the initial recharge rates. The observed inter- and intra-year variability is due to the groundwater levels that strongly influence gravity recharge heads and lateral groundwater flows, as well as the source water quality, which leads to clogging. The increase in groundwater levels in response to MAR was found to be limited due to the high specific yield and transmissivity of the alluvial aquifer, and, in all but one year, was difficult to distinguish from the overall groundwater level rise due to a range of confounding factors. The results from this study provide the first systematic, multi-year assessment of the performance of pilot-scale MAR harnessing village ponds in the intensively groundwater irrigated, flood prone, alluvial aquifers of the Indo-Gangetic Plain.
Highlights
The inter- and intra-annual variability of water availability, manifesting in extreme flood and drought events, presents a considerable challenge to ensuring water security globally [1,2].This variation in water availability, separated by time and space, co-exists in most river basins globally [2]
The first UTFI pilot trial in the Indo-Gangetic Plain in India was capable of recharging an average annual volume of 44,000 m3 with the recharge volume over three years varying from 26,000 to 62,000 m3 (i.e., 430 to 775 m3 day−1 during the recharge periods)
High intra-year variation, reflected in recharge rate reductions ranging from 72.4% to 95.7% relative to the starting conditions, was observed
Summary
The inter- and intra-annual variability of water availability, manifesting in extreme flood and drought events, presents a considerable challenge to ensuring water security globally [1,2].This variation in water availability, separated by time and space, co-exists in most river basins globally [2]. The inter- and intra-annual variability of water availability, manifesting in extreme flood and drought events, presents a considerable challenge to ensuring water security globally [1,2]. The impact of water variability is magnified in the agriculture sector due to its strong dependence on climate. This is exemplified by the fact that of the total loss of USD 80 billion in crop and livestock production in 67 countries between 2003 and 2013, due to 140 medium-to-large-scale disasters (including non-water related events), 83% was caused by flood or drought [3]. Water 2020, 12, 1028 increasing rainfall variability and inducing more and severe extreme weather events, the predictability of water availability will further reduce in coming years [4,5], prompting the need for urgent attention to adaptation.
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