Abstract
Total nitrogen (TN) and total phosphorous (TP) are the main pollutants affecting the water quality of the Miyun Reservoir, Beijing. However, few studies have been conducted on their responses to implemented soil conservation measures at a slope scale in northern China. To explore the impact of soil conservation measures on TN and TP losses, field monitored data from 18 runoff plots under natural rainfalls were used to analyze the changing characteristics of runoff, soil loss, and nutrient losses during 2014–2019. The results indicated that runoff, soil erosion, as well a TN and TP losses from the plots varied significantly, depending on land use and soil conservation measures. Bare plots suffered the highest soil, TN, and TP losses, followed by cultivated plots without soil conservation measures, cultivated plots with contour tillage, and other plots. Event-averaged runoff and soil loss rates ranged from 0 to 7.9 mm and from 0 to 444.4 t km−2 yr−1, and event-averaged TN and TP losses from cultivated plots were the highest, with values of 39.8 and 3.0 kg km−2, respectively. Bare and cultivated plots were the main sediment and nutrient sources. Among the cultivated plots, the terraced plot had the lowest soil and nutrient losses. The vegetated plots had insignificantly lower soil and nutrient losses. Most TN and TP were lost in particulate status from the plots, especially from the plots with soil conservation measures. Soil conservation measures can effectively prevent TN and TP losses. To guarantee water resource use, contour tillage is preferred for the bare and cultivated lands in the study region.
Highlights
Soil conservation measures are widely used in the world to control soil loss and to protect water quality and water resource use because they can reduce both on-site land degradation and off-site sediment siltation [1,2,3]
The Miyun Reservoir is the largest reservoir in northern China which provides around 73% of the total drinking water for Beijing [9]
This study was conducted at an experimental station in the Shixia catchment (117◦4 30 E and 40◦34 40 N) which is located in the upstream of the Miyun Reservoir, Beijing (Figure 1)
Summary
Soil conservation measures are widely used in the world to control soil loss and to protect water quality and water resource use because they can reduce both on-site land degradation and off-site sediment siltation [1,2,3]. The Miyun Reservoir is the largest reservoir in northern China which provides around 73% of the total drinking water for Beijing [9]. In recent years, both runoff and sediment discharge have significantly decreased, and sediment discharge into the Miyun Reservoir has declined from around 100 tons per year in 1954–1959 to nearly zero since 2005, due to human activities and decreased precipitation [10,11,12]. Nonpoint source (NPS) pollution, especially nitrogen and phosphorous pollution, greatly affect the water quality of the Miyun Reservoir
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