Diagnostic Analysis of Farmers' Skimming Well Technologies in the Indus Basin

The short canal water supply has forced the farmers to extract groundwater for irrigation purposes. Farmers are using skimming wells (both single- and multi-strainers) to supplement their canal deliveries. To ensure sustainable groundwater extraction, proper design and operational guidelines for these skimming wells are required. The starting point of such guidelines is to see the extent and existing practices of skimming well technologies. For this purpose, a field survey was conducted in the Indus Basin of Pakistan to see the farmers' groundwater extraction practices and associated problems. Participatory rural appraisal (PRA) identified several design and operational problems with farmers' skimming wells. These include; (i) depth of well, (ii) number of strainers, (iii) horizontal distance of strainers, (iv) priming, (v) water quality, (vi) sand in pumped water, and (vii) reduction in well discharge with passage of time. To investigate these problems, diagnostic analysis was carried out at the reported farmers' tubewells. A test borehole was suggested to get water quality samples along the aquifer depth. The depth of well then was decided on the basis of these water quality analyses. To decide the number of strainers, a pumping test was conducted at test borehole to estimate the contribution of individual strainer and then the numbers were increased according to the desired discharge. Similarly, placing non-return valve between blind pipe and strainer solved the priming problem. The data showed that continuous operation of a skimming well for 12 to 14 hours reduced the well discharge up to 30%. The study showed that there is an imperative needs to develop proper design and operation guidelines for skimming wells, and the farmers and local drillers are the target groups to be trained for sustainable groundwater extraction the Indus Basin of Pakistan.