Climate change is a multidimensional phenomenon, which has various effects on people's environmental and socioeconomic conditions. In the agricultural economy that is susceptible to natural changes, its impact is more profound. Therefore, climate change directly affects society in different ways, and society must pay a price. Climate change, especially the changes in annual temperature and rainfall, has attracted widespread attention worldwide. The variability of these factors or the magnitude of fluctuations varies according to location. Therefore, in the context of climate change, especially in countries dominated by rainfed agriculture, studying the trend of meteorological variables is essential to assess climate-induced variations and propose feasible adaptation approaches. Focusing on this fact is the main goal of this research study was to determine the rainfall trend and the accuracy of predicted temperature at three particular stations of Khyber Pakhtunkhwa (Kp) Province, Pakistan. For this purpose, rainfall and temperature data were provided by Pakistan Meteorological Department (PMD), Islamabad, for the period 1960–2020. Two types of nonparametric techniques, Sen’s slope estimate and the Mann–Kendall test, were applied to determine a trend in the average monthly and annual rainfall. The results of the annual rainfall trend analysis showed that Peshawar and Dera Ismail Khan stations showed a positive increasing trend, while the monthly rainfall trend showed a negative decreasing trend for all stations. The trend was statistically significant for Peshawar and Saidu Sharif stations. The accuracy of predicted and actual temperature and rainfall indicated that mostly over-forecast occurred at Saidu Sharif and Peshawar. Most of the precipitation and temperature records showed under forecast for Dera Ismail Khan, but some over-prediction has also occurred.Graphical abstract

Background: Reservoir sedimentation poses a significant challenge to water resource sustainability, as it reduces storage capacity, compromises hydraulic performance, and shortens the operational lifespan of dams. In Pakistan, many reservoirs face accelerated sediment accumulation due to steep catchment slopes and intensive land use, yet limited research has focused on the role of auxiliary dams in mitigating these effects. Objectives: This study aimed to assess the environmental impact of the Auxiliary Kandar Dam on extending the lifespan of the Main Reservoir in District Kohat, Khyber Pakhtunkhwa. It sought to quantify sediment deposition, evaluate trapping efficiencies, and model future storage scenarios under different auxiliary dam construction timelines. The research addressed a key knowledge gap regarding how auxiliary dam construction can optimize sediment retention and improve reservoir sustainability in semi-arid regions. Methods: A detailed grid survey was conducted to determine the storage capacities of both reservoirs, with volumetric and spatial analyses performed using SURFER software. Sediment yield estimations were calculated through the HR Wallingford Sediment Yield Prediction Model (WSYPM). Field observations, hydrological data, and chronological sediment records were integrated to validate trapping efficiencies and predict future capacity loss scenarios. Results: The initial capacities of the Main and Auxiliary Dams were 1,000,365 m3 and 1,994,974 m3, respectively. Over nine years, the Auxiliary Dam accumulated 196,654 m3 of sediment, resulting in a 9% loss in storage capacity. The Main Dam exhibited a trapping efficiency of 90.48%, which declined with a decreasing inflow ratio from 0.508 to 0.194. Within six years, approximately 175,501 m3 of sediment were deposited in the Main Dam, causing a 61.78% reduction in total storage capacity over 41 years. The observed sedimentation patterns closely matched WSYPM predictions. Importantly, the construction of the Auxiliary Dam in 2014 extended the Main Dam's effective lifespan by 34 years (2022 – 2056). Modelling suggested that additional auxiliary structures in 2016 or 2022 could further prolong the lifespan by 80 years (2022 – 2102) or 68 years (2022 – 2090), respectively, while a proposed left Auxiliary Dam (2025) would extend it by 66 years (2022 – 2088), yielding an overall operational duration of 107 years (1972 – 2079). Conclusion: The findings confirm that the construction of the Auxiliary Kandar Dam significantly reduced sediment inflow into the Main Reservoir, effectively extending its operational lifespan and ensuring sustainable water storage for the region. The study successfully demonstrates, for the first time in this geographic context, the quantitative relationship between auxiliary dam placement and sediment reduction efficiency.