Serious soil and water loss affects the economy and the living quality of the population in faulted basins. Since 2002, China has carried out large-scale ecological restoration projects in karst areas. However, the karst faulted basins have experienced complex climatic changes, which makes it difficult to assess the ecological restoration effects quantitatively. Using the improved Budyko model, basin factor (n) and sediment content factor (C) were divided into climate influence and ecological restoration influence by second-order approximation, and the change ratio of climate influence and ecological restoration on sediment yield and loss was quantitatively calculated in the representative basin of the Nandong Underground River System (NURS). This was carried out in order to effectively distinguish the effects of climate change and ecological restoration on runoff and sediment change in the NURS. Furthermore, this study sought to understand the mechanism of runoff and sediment change and to evaluate the ecological restoration in the faulted basin to provide a scientific basis for the next stage of soil and water conservation policy formulation. The results showed that: (1) Using Pettitt to test the abrupt change of water and sediment in the NURS from 1987 to 2018, we found that 2002 was the abrupt change year of water and sediment in the basin. Before and after the mutation, the runoff and sediment yield decreased significantly, with the change rates of −15.5% and −51.8%, respectively. The decrease in precipitation and the increase in E₀ were not significant, which were −4.5% and 1.4% respectively. (2) By calculating the correlation coefficient and the double logarithm function, it was found that the maximum temperature is the main climatic factor affecting the underlying surface factor n, and precipitation is the main climatic factor affecting the sediment concentration c. (3) Climate change reduced runoff by 77.6%. Ecological restoration has reduced sediment by 51.3 percent. The sensitivity of runoff to maximum temperature was 3.61. The sensitivity of grain yield to precipitation and NDVI was 5.37 and 3.26, respectively. The results show that climate is the main factor of runoff reduction, and ecological restoration is the main factor of sediment reduction. Ecological restoration has greatly reduced sediment production, and ecological engineering has made remarkable progress. However, the reduction of runoff caused by climate change should be paid more attention. The results of these studies will help to better formulate land use management policies for soil and water conservation.

Since 2008, soil and water treatment and ecological restoration have been applied in the karst areas of Southwest China, but the effect of the treatments in karst fault basins is not clear. As a typical watershed of a faulted basin, studying the influence of landscape pattern changes on runoff and sediment yields in the Nandong underground river system (NURS) helps to establish the relationship between watershed and runoff and sediment changes. It provides a theoretical basis and effective method for water and soil management assessment, and soil and water treatment in karst fault basins. The vegetation topographic factor (VTF) was constructed using the normalized vegetation index (NDVI), digital elevation model (DEM) and water-system map from 2000 to 2018. On the basis of VTF classification, the vegetation topographic landscape index (VTLI) was calculated using the FRAGSTATS software, and the effects of VTLI changes on NURS runoff and sediment yield were analyzed. The study found the following: (1) PD, IJI, LSI and SHDI were positively correlated with runoff and sediment yield (p < 0.01), and the correlation coefficients were 0.693, 0.668, 0.551 and 0.582 and 0.62, 0.635, 0.627 and 0.63, respectively. AI and CONNECT were significantly negatively correlated with runoff and sediment yield (p < 0.01), and the correlation coefficients were −0.551 and −0.596, −0.627 and −0.446, respectively. The LPI and DIVISION index were not significantly correlated with discharge, but were significantly correlated with sediment yield (p < 0.05), and the correlation coefficients were −0.179 and 0.271, respectively. (2) The interpretation of VTLI for runoff increased from 0.639 to 0.778, and the interpretation of sediment transport decreased from 0.809 to 0.613. (3) In urban areas, VTF decreased and was persistent. VTF increased in the basin mountain edge area. In mountainous areas, VTF was unchanged, but has an antipersistence trend. The NURS ecological restoration project had achieved obvious results, and the change in the watershed increased runoff production and reduced sediment production. The capacity of soil and water conservation in the high slope area of the mountain edge of the basin recovered and showed a trend of sustainable development. Due to the urban expansion brought about by economic development, the capacity of soil and water conservation around the city has declined, and it showed a sustainable development trend. Policymakers should strengthen the ecological environment of urban areas and coordinate development within mountainous areas.

Wastes from social economic activities had great impact on water quality thereby limiting water usability for domestic purposes. Sewages discharge from people activities, usually consist of undesirable concentrations of soluble chemicals that infiltrate into the surrounding surface and underground water, and then constitute health risk to the populace. In order to investigate the concentration characteristics and health risk for the local residents in Nandong Underground River Watershed (NURW), eleven common heavy metals in the water body analysis were conducted. Health risk assessment (HRA) was taken to analyze eleven heavy metals of 84 water samples from surface and underground waters in NURW: 36 samples underground water and 48 samples surface water. Our results showed that the heavy metals concentration order is that of Fe > Al > Mn > Zn > As > Cd > Pb > Cr > Ni > Cu > Hg. Correlation analysis indicates that these eleven metal elements have certain similarity on material source and migration transformation. The health risks for local residents exposed to metal elements in the water of NURW mainly from carcinogenic risk (10−6～10−4 a−1) through drinking way, and the health risk of heavy metals exposed to children through drinking way was much higher than adults. The maximum exposing health risks of Cr in both underground and surface water were higher than the recommendation standard (5.0×10-5 a-1) from ICRP, and all the values over the standard (5.0×10-6 a-1) recommended by the Swedish Environmental Protection Agency and the Dutch Ministry of Construction and Environment and the British Royal Society. The results of health risk assessment shows that Cr in the water of NURW was the mainly source of carcinogenic risk for the local residents, following by Cd and As. Consequently, it is necessary to control the three carcinogenic metals when the water was used as drinking water source.