Influence of land use on nitrate concentrations in baseflow in a rural watershed of Three Gorges Reservoir Area, China

In this paper, the relationships between nitrate (NO3--N) concentrations in baseflow and land use were studied in a rural watershed of Three Gorges Reservoir Area from 2004 to 2006. The results indicated that NO3--N concentrations ranged from 0.4 to 14.6 mg L-1 and were significantly higher in autumn and winter. Analysis of variance indicated that there was significant difference in NO3--N concentrations among seasons and sampling points. In addition, an interannual increasing trend was found in the study period. Moreover, regression analysis revealed that NO3--N concentrations significantly correlated with the proportions of paddy field and orchard in the subwatersheds, while woodland had positive effect for preventing NO3--N loss. Paddy field has more contribution to NO3--N concentrations compared to other land use types. The results indicted that the baseflow is one of major pathways of NO3--N losses, and agricultural land use strongly influences NO3--N concentration in stream water in rural watersheds of Three Gorges Area. Therefore, it is indispensable to adjust land use structure and agricultural activities for water source protection in Three Gorges Reservoir Area, China.