Artificial Recharge and Sustainable Management of Groundwater

By: K C Naik, S K Verma, J R Verma and M M Sonkusare
With the increase in demand, withdrawal of groundwater has increased manifold over past few decades resulting in the long-term decline in groundwater levels. A higher rate of withdrawal over several years with heavy pumping coupled with rapid urbanisation has reduced the natural recharge of aquifers. Rainwater harvesting and guiding the non committed surface runoff to a depleted aquifer are ideal solutions for mitigating the problem.
Magazine Articles Water

Chhattisgarh with nearly 4 per cent of the country’s area is the 10th largest state of India with a population of 2.6 million (Census 2011). Physiographically, it consists of plateaus of Bastar in the south, plains in the centre and hills in the north. Chhattisgarh experiences a subtropical climate with mean monsoon rainfall of 1240 mm. The main rivers of the state are Mahanadi and its tributaries Seonath, Hasdeo Mand and Arpa which drains the western, central and northern part. The river Indravati and Sabri, tributaries of Godavari drain the southern part, while Son, a tributary of the Ganga drains the northern part. Other minor basins include Narmada and Brahmani. Geologically, Chhattisgarh comprises of litho units ranging in age from Archaean to Recent. Nearly 58 per cent of the State is covered by crystalline and metamorphic rocks, around 27 per cent by rocks of Chhattisgarh group of basins, nearly 12 per cent by semi-consolidated Gondwana sediments and remaining 3 per cent by Deccan Traps, lameta, laterites and alluvium. Groundwater occurs under unconfined condition in phreatic aquifers and under semi confined to confined conditions in the deeper aquifers.

Chhattisgarh, an agrarian economy, depends upon groundwater as monsoon is fairly erratic in the area. Although not alarming yet, a growing stress on the groundwater resources needs to be mitigated in order to achieve sustainable development of the resource.

The computations of sub-surface storage

Based on the data of National Hydrograph Stations established by the Central Groundwater Board, a map of the decadal mean post-monsoon depth to water level is computed. A trend analysis was carried out for the decade between 1999 and 2009. A total of 22401 sq km in Chhattisgarh shows a declining trend in the groundwater levels. In these areas the rate of decline is more than 0.1 m/year, which covers about 16.5 per cent of the total area of the State. Deeper water level i.e. more than 3 metres below ground level (mbgl) during the post-monsoon period and declining trends were demarcated for artificial recharge. An estimated amount of Rs 19927.28 million is planned towards the cost, which includes detailed study of the area and planning, construction and maintenance of the suitable artificial recharge and rain harvesting structures.

Sub-surface storage and water requirement

The estimated sub surface storage is shown in Fig 1. It is based on average post- monsoon depth to water level for the period 1999-2009. The decadal post monsoon average depth to water level is in the range of 3 to 6 mbgl. Based on this map the volume of unsaturated zone available for recharge (vadose upto 3 mbgl) was calculated for each district. A total of 55962 million cubic metre (mcm) volume of unsaturated zone was estimated for Chhattisgarh, which gives a sub-surface storage potential of 1430.95 mcm calculated based on the specific yield of the rock types in the watersheds. The requirement of water to fully saturate the vadose zone upto 3 mbgl was worked out for each watershed at 75 per cent efficiency. The total requirement of water to saturate the sub-surface storage space worked out to be 1903.16 mcm for the entire State. The priority areas for the artificial recharge is shown in Fig 2. The total quantum of source water, which can be utilised for creation of this sub-surface storage worked out to be 37783.48 mcm for the state.

Fig 1. Ground Water Trend and Fig 2. Area Identified for Artificial Recharge
Fig 1. Ground Water Trend and Fig 2. Area Identified for Artificial Recharge

Runoff characteristics of catchments

The co-efficient of the mean annual runoff for catchments range from 22 to 43 per cent and the total runoff is about 37783.48 mcm. This surplus water, if stored in reservoirs, can be used during lean periods. During monsoons, the surplus water, which causes floods in some areas, can be effectively diverted to the groundwater recharging zones. There is vast potential for development of medium, small, mini and micro irrigation projects. The development network of storage reservoirs and groundwater recharge at all possible storage and distribution system has been conceptualised as sustainable sources of water supply.

Type of recharge structures and cost estimation

The suitable artificial recharge structures in the State are gully plugs, gabion structures, contour bunds in the upper reaches of the watersheds, percolation tanks, nala bunds in the runoff zones and recharge shafts, gravity head wells in downstream areas. There are 102 urban areas in Chhattisgarh, which cover an area of 200.54 sq km with total number of houses around 4.19 million. Due to the scarcity of water, individual houses in most of the urban areas have constructed wells/ bore wells. However, this unplanned withdrawal of groundwater has resulted in lowering of water levels and dwindling of yield/drying up of wells. The availability of rooftop in urban areas is an attractive solution for the collection of rainwater during the monsoons for recharging of the groundwater reservoir. Given the varied hydro-geological milieu even if 25 per cent of the houses with an average roof area of 50 sq m are considered, a total roof area of 6.5402 sq km is available to collect the rainfall which works out to be about 7.952 mcm; about 90 per cent of this can be used for recharging groundwater.

Cost estimates and benefits

Based on the hydro-geological situations of each area, a total number of 87228 artificial recharge structures have been proposed, with a total cost of Rs 18619.23 million. And, for urban areas the roof top rainwater harvesting have been planned with a total cost of Rs Gr1308.05 million. The benefit from the proposed plan would be in terms of creation of additional irrigation potential in rural areas and supplementing drinking water needs in urban areas. An additional irrigation potential of 206188.76 ha can also be created. In urban areas, the roof top rainwater harvesting will cater to the annual drinking water needs of additional 0.36 million persons. Based on conceptual framework, the detailed feasible account of artificial recharge in Chhattisgarh has been worked out. The management plan to recharge the groundwater can hugely benefit the State and lead it to long term sustainability.

Tirathgarh

Located in the Bastar district, at a distance of 35 km from Jagdalpur the milky waterfall is a treat for explorers and nature lovers. It can be approached through the state highway of Jagdalpur to Sukma. The waterfall is situated in Kanger Valley National Park at a height of approximately 300 ft – originating from the river Mugabahar. This place is a favourite resort for groups looking for a day-long picnic in a forest. The good season for visiting these waterfalls is from October to February. The nearest airport and railway head is Raipur around 330 km from the falls.

Amrit Dhara

Amrit Dhara is a waterfall located in Koriya district on the Hasdo River and is about 7 km from Nagpur on the Manendragarh-Baikunthpur road. About 80 to 90 feet high and 10 to 15 feet wide, it creates a beautiful misty ambience and the best time to visit it is during the monsoons from June to August. Close by is a Shiv Temple where every year, since 1936, the Mahashivratri fair is organised – known to have started by Ramanuj Pratap Singh Judeo, the King of Koriya. The nearest airport is Raipur which is 232 km, while the nearest rail head is Manendragarh. From here one can take a bus or taxi to Nagpur, and hire a taxi to the fall.

 

 

Leave a Reply

Your email address will not be published. Required fields are marked *