Water Tech For Agriculture
Managing localized water stagnation and improving ground water quality
The five villages (Mundri, Geong, Kathwar, Sampli Kheri and Bhaini Majra) in Kaithal district of Haryana have been adopted under Farmer FIRST Project “Empowering farmers through selected interventions in salt affected agroecosystems of Ghaghar Plains”. Kaithal district in general and these villages in particular have major limitations of poor quality groundwater (high RSC>2.5 meq/l) and soil sodicity (soil pH>8.2) reducing soil infiltration rate and submergence of crops during the periods of intense rains resulting in crop failure. To provide location specific drainage-cum-recharge facility for safe disposal of excess rain water in low lying areas where runoff gets accumulated and adversely affects the crop production, cavity type groundwater recharge structure was installed. The recharge cavity consisted of conventional cavity tube well coupled with sand-cum-radial filtration unit, constructed by drilling a bore hole until a sandy layer found below a clayey layer. A high pressure (10 kg/m2) blind PVC pipe of 9'' (22.5 cm) f was drilled upto 210 feet soil depth into the clay layer and sand was pumped out until a stable semi-spherical cavity was developed.
Impact: Point observations through periodic water monitoring indicated rise in ground water table (upto 1 m) during the monsoon period (July-September 2017) beneath the recharge structure and improvement in ground water quality with concomitant reduction in residual alkalinity in irrigation water (RSC: 1.5-2.5 meq/l). Piezometers have been installed at a distance of 10, 30 and 50 from the main unit to further monitor the spatio- temporal improvement in water quality. Heavy downpour during the last week of June 2017 (150 mm on a single day) during the last week of June 2017 immediately after rice transplantation resulted in complete crop submergence (Fig. 1a). The installed structure reduced flood volumes through drainage-cum-recharge structure and saved transplanted rice crop (Fig. 1b) in lowest 5 ha area, though low to modest impact was also clearly visible in the surrounding areas.
Economics: The total cost of the structure at the selected site was about 2.5 lacs @ Rs 1200/ft approximately depending on the lithology of the area. Considering the re-transplantation cost for rice in 5 ha area and 15-25% potential yield reduction under delayed transplanting, the tangible benefit through direct saving was estimated to be Rs. 30000-35000 /- in lieu of transplanting (nursery + labour cost) and income loss of approximately Rs. 80,000-90000/- in absence of recharge structure.
The payback period for the selected intervention is estimated to be 2-3 years with net present value (NPV) of approximately Rs. 1.34 lacs, benefit-cost ratio of 1.25 and internal rate of return (IRR) of 19% indicating the desired economic feasibility of investment on drainage-cum-recharge structure as well as for augmenting ground water, improving its quality (reduction in alkalinity) through recharge of excess water and enhancing farmers income by saving submerged rice crop during the period of intense rains.