Comparison of Groundwater Table Depth, Drainage Coefficient, and the Determination of Nutrient Losses in the Salinity Control and Reclamation Project (SCARP) Mardan, Pakistan
摘要
A well-designed subsurface tile drainage system plays a crucial role in reclaiming waterlogged areas and minimizing nutrient losses. The purpose of this study is to investigate the performance parameters of the composite drainage system and nutrient losses in the Mardan Salinity Control and Reclamation Project (SCARP), focusing on monthly water table depths, drainage coefficients, soil properties, and seasonal variations in mineral ion concentrations. The study collected data through field experiments, lab analyses, and simulation models to monitor performance parameters such as drainage efficiency, groundwater fluctuations, and soil moisture levels. Additionally, nutrient losses—specifically nitrogen and phosphorus—were measured using soil and water sampling techniques. The results indicated that the water table depth remained relatively stable from December to April, mostly above 2 m, which was sufficient to prevent waterlogging. Drainage coefficients varied among the three collectors, with the highest value recorded in March (2.69 mm/day), corresponding to increased rainfall. The Sodium Adsorption Ratio (SAR) showed significant variation across different locations and depths, ranging from 4.05 to 9.19, highlighting spatial and vertical differences in soil salinity. Seasonal nutrient losses revealed higher concentrations of Sodium (64.75 mg L−1), Calcium (32.85 mg L−1), and Magnesium (14.70 mg L−1) in March, due to increased irrigation. Phosphorus losses, though uncertain, were still significant for long-term water quality, while potassium losses peaked at 6.69 mg L−1, indicating potential nutrient depletion. Micronutrient losses for Copper (0.40–0.48 mg L−1), Manganese (0.15–0.63 mg L−1), and Zinc (0.03–0.06 mg L−1) were within acceptable agronomic ranges, with minimal Iron losses. Ammonia (2.40 mg L−1) and nitrate (0.63 mg L−1) losses were highest in the drainage water, particularly in April and May, respectively, and were linked to fertilization practices. The composite drainage system in the Mardan SCARP effectively mitigated waterlogging but poses challenges in nutrient management. The study highlighted the need for integrated management practices that balance drainage efficiency with nutrient retention. Adopting improved drainage techniques and soil management practices could enhance both agricultural productivity and environmental sustainability in the region.