Evaluation and application of the management priority of soil erosion in small watersheds

Soil erosion has caused a heavy threat to agriculture production in China at the present stage. The accurate identification of priority small watersheds is one of the most important tasks for implementing control and prevention in batches. However, it is still lacking in the intelligent decision-making and implementation of soil loss control at present. Among them, the severity of soil erosion is an important indicator of priority small watersheds. Previous studies have been focused on the simple and single indicator during evaluation and consideration. Many subjective factors have also made the evaluation complex and less accessible. Therefore, it is very urgent to identify the management priority for the scientific, reasonable, and efficient application of soil loss control for better conservation. This study aims to evaluate the management priority of soil erosion control in small watersheds. The key area of soil erosion was selected at Zigui County in the Three Gorges Reservoir Area. The double goals were taken as the 'reduction and degradation 'of soil and water loss. Two dimensions were also integrated with the soil and water loss area and soil erosion intensity. The results show that the current soil and water conservation rate in 2021 was 69.12%, and the long-term (in 2050) soil and water conservation rate was 81.74%, with an overall increase of 12.62 percentage point. The soil erosion modulus in 2021 was 758.50 t/(km²·a) at present, where the minimum modulus of soil erosion was 408.71 t/(km²·a) with an overall decline ratio of 46%. However there were great differences among the soil and water conservation rates under current and long-term situations, as well as the current and the minimum soil erosion modulus in each small watershed. The long-term soil and water conservation rate and the minimum soil erosion modulus were generally similar to the spatial distribution, compared with the current. But there were great changes in some areas and values. Most areas shared a large potential for the soil and water conservation rate, as well as the soil erosion control degree. Erosion plots were widely distributed to be completely managed and downgraded, especially in the small watersheds in the central and western parts of the county. Large areas were found for the soil erosion area abatement and soil erosion intensity downgrading. The spatial distribution pattern was observed in the priority of soil erosion control in each small watershed: high in the central part, while relatively low in the eastern and southern parts. The number of small watersheds with a management priority greater than 0.6 accounted for 11.76% of the total. The management priority can be expected to cover both soil erosion area and soil erosion intensity. The goals and the relative size were determined for their reduction space. An accurate and rapid detection can also be achieved for the decision-making on the small watershed. The finding can provide technical support to identify the priority of soil corrosion in small watersheds.