Characterization of aquifer hydraulics and pumping well yield for supplemental paddy crop irrigation using pumping tests in Perak, Malaysia

The escalating magnitude of challenges faced by human beings globally, including insufficient water management, climate change, water pollution, and drought, has resulted in water scarcity, especially in isolated regions in Malaysia (insufficient amounts of water for irrigation). This research brought attention to the need for groundwater as an auxiliary resource for paddy irrigation to counteract the alarming trend of the rice bowl shrinking in Labu Kubong, Perak. Therefore, this research aimed to quantify subsurface aquifer characteristics, including transmissivity (T), hydraulic conductivity (K), and storativity (S), and to estimate potential well yield using a series of in-situ pumping tests (step drawdown, constant discharge, and recovery rates) in the years 2020 and 2021. The step drawdown results showed that the specific capacity averaged 0.425 m²/hr, and the well efficiency ranged from 59% in 2020 to 41% in 2021, indicating that the well has low capacity, possibly due to poor construction, the effects of drawdown on discharge rates, and varying soil types. The constant discharge rate findings indicated average T values of 7.84 m²/day, classified as an intermediate class, which showed a low to intermediate productivity borehole. Further, the S was observed as 0.00345 (2020) and 0.0763 (2021) using Cooper and Jacob’s assumption, one order of magnitude larger than the previous S in 2020, suggesting a confined aquifer to semiconfined aquifer. The quantification of the K ranged from 0.432 to 0.576 m/day, suggesting that the alluvial formation contains fine to coarse media. Furthermore, the potential well yield was obtained at 194 m³/day, which was sufficient to meet the irrigation requirement of a 1.5 ha paddy plot (107 m³/day). The overall findings revealed that the aquifer system was suitable as an auxiliary groundwater resource for the paddy plots due to the tropical region’s naturally abundant water supply, especially for paddy irrigation.