The status of groundwater resources in the command area of one of the oldest dams of India: The Hirakud Dam
As discussed in the last newsletter (2nd issue), the groundwater thematic group has carried out exclusive field visits in the Mahanadi basin to understand the groundwater status in the region. The Hasdeo-basin was discussed in detail in the last issue. The current issue exclusively deals with the groundwater status in the command area of the Hirakud dam.
The Hirakud dam is the first major dam built post-independence in India and the only large dam on the Mahanadi River. The multipurpose dam was constructed for flood control, irrigation and power generation. However, the dam has been surrounded in controversies since its inception. Many conflicts have been reported in this region, considering the livelihood of the people dependent on the waters of Hirakud dam.
The command area of the Hirakud dam can be divided into three broad parts;
1) Area irrigated by the Sason Canal
2) Area irrigated by the Bargarh canal and
3) Area between these two main canal systems.
The region was earlier dependent on traditional tank systems, and dug wells were not very common. Drawing from the experience from other parts of Eastern India with similar geology, it can be stated that, often, these tank systems are a combination of surface water and groundwater (most tank systems in similar hard rock typologies are actually perched aquifers formed by localised weathering of the hard rocks). Two types of tank systems exist in these areas;
• ‘Kanta’: This is a small earthen dam which impounds water, often covering tens of acres
• ‘Bandh’: This is a small pond created by impounding water by way of bunding it on four sides
These traditional tank systems have fallen into disarray after the management of the tanks was taken over by the Government. The government has licensed these tanks for fisheries. Further, the advent of tube wells, as a source of community (and private) drinking water, has further diminished the use of tank systems.
As one traverses towards the south of the command area, one can observe that the traditional groundwater use in the form of dug wells increases. Traditional community dug wells are more common in villages covered under the Bargarh canal system; however, tube wells are the most common source of drinking water all over the command area of the Hirakud dam.
Groundwater quality in shallow aquifers is of grave concern, throughout the command area. Salinity values in shallow aquifers were observed to be in the range of 1500 mg/l. The standard for safe drinking water is 500 mg/l. The quality in deeper aquifers tapped by tubewells was found to be within the limits set by the Indian drinking water standard.
Paddy is the dominant crop in the entire Hirakud command area. Farmers in areas with good canal coverage cultivate two paddy crops in a year, while areas with partial or poor coverage have single paddy crop.
The salinity in the shallow aquifer could be a result of the over use of fertilisers for paddy cultivation, or due to natural salinity as a result of the weathering of the hard rocks. This can be investigated further by conducting detailed water quality tests. The shallow aquifer shows quick recharge and high storage capacity but also discharges quickly. This is observed in the dug wells that fill up to their capacity post monsoon and show rapid fall in water levels, often almost drying up in summers. Most of the areas show thick weathered profiles of upto 10m.
Development of groundwater
Majority of the command area shows very little groundwater development for irrigationpurposes. But, within the command areas, certain trends are emerging, these are as follows;
The hydrogeology of the area is a naturally limiting factor which has not allowed the proliferation of borewells as yet. Based on limited field checks, it can be stated that most of the command area consists of fractured hard rock systems. However, the fracturing is not even throughout the area and often is localised. Thus, borewells frequently fail to tap aquifers and the high cost of drilling and procuring electrical connections have prevented private borewell proliferation thus far
The Government of Odisha scheme, ‘Biju Krushak Vikash Yojana-Deep Borewell Secha karyakrama’ is providing borewells to farmers at 10% of the actual cost of drilling, pump system and electrical connection. Many farmers have taken benefit of this scheme and have obtained the borewells. Full-fledged irrigation will begin once the pumps and electrical connections are in place
In areas close to the Sason canal (the northern portion of the command area) farmers with access to some groundwater irrigation opt for vegetable cultivation. While, farmers with access to groundwater irrigation near the Bargarh canal system opt for paddy cultivation
Areas close to Attabira require a separate mention in the Hirakud command area. This area produces very high quantities of paddy largely dependent on canal irrigation. However, this area also shows the maximum groundwater based irrigation for paddy cultivation as compared to all other areas in the command area. A small area of about 2 km2 has almost one borewell per farmer. The groundwater use in this part is very high – wells are operated for almost 15 to 20 hours for 250 days every year for cultivating two paddy crops in an area where canal water does not reach. Most of these borewells are private indicating that the high paddy yields based on canal water have enabled farmers to fund private groundwater sourcing
The locals’ term the areas outside the canal irrigated areas as ‘drought’ areas although these are high rainfall areas. The term drought is used to indicate the unavailability of surface water. Most of these areas also face a drinking water crisis as borewells and hand-pumps dry up during summer. Although the Hirakud command area does not show the amount of groundwater development as that observed in the Hasdeo-Bango basin or the Mahanadi delta area, drinking water supply is still largely groundwater dependant. Pockets of groundwater dependant areas have started to emerge due to the natural inequalities formed by the inhomogeneous hydrogeological setup as well as due to the socio-economic conditions.
The next issue of the newsletter will detail the observations in the Mahanadi delta with regards to the status of groundwater.