Abdul Wahab Khan
Panaji: Despite having 50% of the land as forest area and receiving over 3,000 mm of annual rainfall, the tribal villages of Gaondongrim and Cotigao in Canacona taluka experience severe water scarcity in the summer months, with a study attributing this annual crisis to the area’s challenging topography.
Conducted by the Central Ground Water Board, the aquifer management study states that the groundwater sources in these villages dry up from March to May, leaving the communities struggling for basic water supply.
The research team, led by scientists Sangita Bhattacharjee and Sushant Navarat, discovered that the problem lies in the geography of the area with elevation ranging from a towering 839 metres above mean sea level in the northeastern hills to just 13.8 metres in the southwestern plains, creating steep gradients where slopes reach between 30 to 60 degrees.
“Due to geomorphological constraints, there is increased surface runoff with minimal infiltration,” the report states. The highly permeable lateritic soil, which dominates the terrain in the villages, allows the recharged groundwater to escape rapidly as baseflow, depleting the shallow aquifers during summer months.
The study employed sophisticated techniques, including monitoring 30 key wells comprising 18 dug wells, five borewells and seven springs, during both, pre-monsoon and post-monsoon seasons. Pre-monsoon water samples were collected from 52 locations, while 58 samples were collected in post-monsoon period for chemical analysis.
The study categorised the aquifer system into two types: Aquifer I, consisting of shallow laterites and weathered meta-basalts ranging from 10 to 45 metres depth, and Aquifer II, comprising deeper fractured meta-basalts and schists extending from 50 to 90 metres below the ground. Many wells reach their base levels and completely dry up during the peak summer, especially those situated away from streams, the study discovered.
An analysis of the water quality in the villages revealed generally potable condition, though localised elevated levels of manganese, iron and copper were detected in certain habitations.
According to the study, an analysis of the demand and supply of water paints a stark picture with the combined population of 8,154 people in the two villages requiring 448.47 cubic metres of water daily at a standard 55 litres per capita allocation, yet only 318.60 cubic metres are currently supplied from the eleven groundwater sources. This creates a deficit of 129.87 cubic metres per day that intensifies during the three-month dry period.
Stating that over-extraction from closely spaced borewells risks aquifer dewatering, while poorly located wells may intersect low-yield zones, leading to well failure, the study warns that continued unregulated extraction could dry up the traditional springs that many hamlets still depend on.
The study report also recommends regulating borewell depth and spacing, protecting spring recharge zones and promoting rainwater harvesting and artificial recharge structures.
The study was undertaken at the request of the state’s water resources department under the National Aquifer Mapping and Management Programme 2.0.
