Background Yunnan province is a mountainous area, with as much as 94% of the total area belonging to this category. There are many high mountains and valleys, complex and diverse climate types, numerous rivers and lakes all in tandem with heavy and concentrated rainfall. Moreover, with the continued impact of human activities, soil erosion has become very serious in Yunnan. Serious soil erosion has caused the decline of land productivity, siltation of riverbed and water bodies, and natural disasters such as frequent floods, drought and debris flow. Controlling soil erosion and improving the ecological environment is an important task for the ongoing ecological construction in Yunnan province.

Methods Based on the monitoring compilation data of soil and water conservation monitoring sites in Yunnan province from 2012 to 2016, 36 soil and water conservation monitoring sites were positioned and divided into soil and water conservation type areas according to the national 3-level division of soil and water conservation. The dynamic monitoring of soil and water loss in the Yunnan province was studied in depth from the aspects of rainfall, runoff and sediment production in runoff field of different land use types and small watershed, non-point source pollution output in runoff field and small watershed, debris flow monitoring.

Results The runoff rates of different soil and water conservation type areas showed as wasteland > sloping farmland > grassland > terrace > garden > forest. The soil erosion moduli were in the order of sloping farmland > wasteland > terrace > garden > grassland > forest. Average annual watershed runoff moduli of different soil and water conservation type areas were 0.12-12.05 L/(s·km²), and the sediment modulus was 6.20-1659.00 t/(km²·a). The average annual runoff moduli of representative hydrological sites were 0.20-10.90 L/(s·km²), and the sediment moduli were 1.28-686.00 t/(km²·a). After constructed contour reverse-slope terrace in sloping farmland, the loss of N steadily reduced 62.78%-86.50%, and the loss of P steadily reduced 50.41%-90.83%. The outputs of total nitrogen concentration and total phosphorus concentration were 2.55-5.23 mg/L and 0.65-1.36 mg/L respectively in the Yizhe small watershed from 2012 to 2016, and the outputs of N amount and P amount were 3.65-15.12 t and 0.95-2.44 t. Short duration torrential rain was one of the important causes leading to debris flow. It was easy to cause secondary debris flow if strong rainfall occurred in a short period after debris flow occurred.

Conclusions This study reflected the basic situation of soil and water loss in Yunnan province, which can provided a basis and reference for the monitoring work of soil and water conservation monitoring sites in the future, and provide a theoretical basis and data support for the prevention and control of soil and water loss.