ABSTRACT Agricultural intensification in East Africa, particularly within the Enkare Narok Catchment in Kenya, poses significant threats to water quality and hydrological stability, yet the efficacy of conservation practices is often complicated by legacy nutrients and water balance trade‐offs. This study aims to use a SWAT model to simulate and calibrate hydrology and water quality, quantify the impacts of various land management scenarios on sediment, nitrogen (N), and phosphorus (P) loads, and evaluate the trade‐offs between water quality improvements and water yield, with a specific focus on legacy nitrogen dynamics. The rigorously calibrated model (NSE = 0.67, R 2 = 0.73, PBIAS = 2.97%) simulated a Baseline scenario, a Conservation scenario (featuring no‐till, filter strips, and riparian buffers), and an Intensification scenario. Results demonstrated that conservation practices dramatically reduced sediment yield from 14,160 to 2844 Mg/year (80% reduction) and phosphorus from 333,068 to 78,782 kg/year (76% reduction), but were markedly less effective for dissolved nitrogen, achieving only an 8% reduction (from 1,954,763 to 1,802,976 kg/year) due to legacy N in groundwater. Furthermore, the Conservation scenario significantly reduced water yield (Q/P from 0.37 to 0.11) by enhancing evapotranspiration from 59% to 87% of precipitation, revealing a critical trade‐off between water quality and quantity. Conversely, intensification increased sediment by 50% (to 21,240 Mg/year) and nitrogen/phosphorus by 30% (to 2,541,192 and 432,988 kg/year, respectively), resulting in a flashier hydrological regime (Q/ P = 0.50, SR/Q = 0.50).
Josué SIMBO (Mon,) studied this question.