Water-Holding Capacity of Seasonal Ponds: A Case Study from Some Selected Areas in North-Western Bangladesh

Abstract: In the drought-prone north-western region of Bangladesh, a large share of ponds are seasonal, retaining water for only part of the year, which severely limits their use for fish culture. This case study assessed the water-holding capacity of seasonal ponds and its physical determinants in selected areas across four districts (Rajshahi, Naogaon, Rangpur and Dinajpur). Forty-five seasonal ponds were monitored over one hydrological year (June–May), with measurement of pond morphometry, bottom-soil texture, monthly water depth, seepage and evaporation. The ponds were small (mean area 0.16 ha) and moderately deep (mean peak depth 1.95 m) and were filled mainly by monsoon rainfall and runoff. Bottom-soil texture varied widely and proved to be the principal control on water-holding capacity. Ponds were grouped by dominant soil texture into sandy-loam (33 %), loam/clay-loam (40 %) and clayey (27 %). Seepage rate fell sharply from sandy-loam (3.18 cm/day) to clayey ponds (0.46 cm/day), and mean water-retention period rose correspondingly from about 5.0 months in sandy-loam ponds to 9.0 months in clayey ponds. Water-retention period was strongly negatively correlated with seepage rate (r ≈ −0.89) and positively with soil clay content (r ≈ 0.84) and pond depth. The results show that improving water-holding capacity—through clay/soil sealing of sandy pond beds, re-excavation to increase depth, and reduction of seepage—can extend the culture period substantially and unlock the productive potential of the region's numerous seasonal ponds.