PANAJI | Dec 04, 2015: A study of the water bodies around the Salaulim dam catchment area, where mining had once been carried out, has pointed to the declining water recharge as well as contamination of the underground water.
The reports of the study were presented at the recently held national workshop on ‘water conservation, water security and water quality’ by the ministry of water resources.
The study ‘hydrogeological evaluation of a watershed with mining activities: case study of Salaulim reservoir, Goa, India’ was conducted by Ashwini Panandiker of The Energy and Resources Institute with A G Chachadi of earth sciences department, Goa University, during the period 2011-12.
The study has said that often a large quantities of groundwater is pumped out for the purpose of open-cast mining; this could lead to water stress conditions if the quantity of groundwater extracted surpasses the total recharge.
Speaking to ‘The Navhind Times’, Panandiker said, “The issue is very sensitive as it concerns an area around the Salaulim dam and also within the location of mines. The study was concluded in 2012 and can be considered as the base study on the subject as such a study has not been conducted earlier around this site.”
The study was carried out on 66 groundwater monitoring wells at Guleli, Kumbhari and Curpem sub-watersheds, an area covering 180 square kilometres and on a reservoir area of 29 square kilometres. The samples were collected and analysed in the laboratory for the physic-chemical parameters such as pH conductivity, total dissolved solids, total suspended solids, iron, manganese, etc.
The researchers have observed that the iron, manganese and TSS concentrations were used as indicators to assess impact of mining.
“The TSS values at locations such as Bhatimal, Neturlim, Curpem, Vichundrem and Jaqui were high as compared to the other locations. Since they are open wells, the possibility of contamination is high,” report has said.
All the three locations at Curpem watershed, which are close to the active and working mines, showed increase in TSS concentration during monsoon season.
According to Panandiker and Chachadi “this could be because erosion potential is more in the area”.
Stating that a new study would be undertaken after resumption of mining activity, chief engineer of the water resources department Sandeep Nadkarni said, “For a comparative and analytical study we will have to identify the abandoned, working and non-working mines. As currently the mining activity is at halt; this can be determined only after mining resumes.”
On the decline in water recharge, the study report has said that a decreasing trend was observed in a well which lies close to the watershed but not within it. Taking this as an indication, judicious development/withdrawal of groundwater in future is warranted. The preliminary observation was that the iron concentration was more at the wells closer to the mine and decreased with the increase in the distance.
The analysis revealed that the average water level fluctuation between the pre- and post-monsoon was found to be 0.97 metres at Kumbhari, 1.06 metres at Guleli and 1.14 metres at Curpem watershed.
“In Curpem watershed, the fluctuations were quite large at one location between Malcopona and Shelpem. This may be due to active mining activities in the area. The groundwater draft would change if more mines are allowed in the watershed,” the report has stated.
The groundwater mainly gets recharged from the forested areas as compared to the low-lying plain areas. It gets discharged in the low-lying paddy fields, reservoir and rivers.
Panandiker and Chachadi have recommended that preventive measures be undertaken for control of soil erosion at sensitive areas around the reservoir along with treatment of raw water for minimizing the negative impact on water quality and reservoir capacity due to sedimentation.
They have further recommended that the working mines should strictly implement all the control measures to prevent water contamination and should adhere to proper management plan at the time of closure.
Demanding that no new mining activity should be allowed in the immediate vicinity of the reservoir, researchers have recommended regular monitoring of surface and groundwater quality and levels.
The researchers through field inspections in 2011 had identified four active mines and seven abandoned mines and also 17 very old non-working mines. All the working and abandoned mines were in the Curpem watershed in the western part of the Salaulim reservoir.
The non-working mines were located in Guleli and Curpem watersheds and two were in the Kumbhari watershed.
(Source: http://www.navhindtimes.in/)