Monitoring and driving force analysis of spatial and temporal change of water area of Hongjiannao Lake from 1973 to 2019

Assessing ecological health in a semi-arid basin: a case study of the Wei River Basin, China

A healthy water ecosystem within a river basin is essential for maintaining ecological security, preserving species diversity, and ensuring sustainable socio-economic development. Unfortunately, human activities have significantly threatened the health of water ecosystems in various basins. Consequently, timely restoration and targeted protection of damaged river ecosystems have become crucial objectives in watershed management. As a prerequisite and cornerstone for river protection and management, assessing river ecological health has emerged as a primary focus in current research. In this study, we selected the Wei River Basin, a representative area of the Yellow River Basin, as our research subject. We identified multiple influencing factors, including society, biology, water quality, and habitat, which collectively impact this semi-arid region. To assess the overall impact of these factors on ecological health, we developed a comprehensive River Ecological Health Assessment Index (REHAI) system. The research findings indicate that the Wei River system, as a whole, is currently in a healthy state, while the Jing and Luo River systems are classified as sub-healthy. Furthermore, we observed variations within the Wei River system itself; the upper reaches of the Wei River exhibit higher levels of health compared to the middle reaches, whereas the water environment in the lower reaches is the most compromised. This degradation can be attributed to downstream subsidence, increased pollution, and rapid urbanization. By establishing a river ecosystem health assessment methodology and conducting a comprehensive evaluation of the health status of river ecosystems, this paper puts forward management recommendations for river basins. These findings provide a scientific basis for the sustainable utilization of water resources in river basins and promote the harmonious coexistence of humanity and nature.

Water resource dynamics and protection strategies for inland lakes: A case study of Hongjiannao Lake

Globally, lakes are drying up and shrinking and inland lakes, in particular, face severe water shortage problems. Thus, the degradation mechanisms and protection measures for inland lakes urgently need to be explored. Hongjiannao Lake (HL), an inland lake on the border of Shaanxi Province and Inner Mongolia Autonomous Region of China, was selected for the present case study. The evolution of HL was analyzed and the current lake water storage was measured on site. The driving factors of water resource changes in HL were discussed based on meteorological and landcover data. The results showed that (1) from 1929 to 2021, the lake area of HL experienced four stages: formation, stability, shrinkage and recovery. The smallest water area was 31.08 km2 in 2015, half the size of lake in the 1960s. (2) Spatially, the morphological changes of HL mainly occurred where the rivers entered the lake. (3) In 2021, the average depth of HL was 3.77 m, and the water storage capacity was 140.56 million m3. (4) The annual average evaporation was 3.36 times the amount of the annual average precipitation in Hongjiannao Basin (HB), but climate change was not the main driver of changes in the HL area. (5) In the past 20 years, cultivated land and artificial surface increased by 3.11% and 1.04%, respectively, whereas grassland and water body decreased by 3.51% and 0.45%, respectively. The expansion of cultivated land and artificial surface, as well as the construction of reservoirs upstream of the lake, hindered the replenishment of water resources to HL. This study recommends a range of strategies for water resource protection in inland lakes, including implementing ecological restoration projects, carrying out inter-basin water transfer measures, improving the efficiency of regional water resource use, and improving industrial structure and distribution.

Comprehensive Evaluation of the Importance of Ecological Land in Arid Hilly Cities in Northwest China: A Case Study of the Core Urban Area of Lanzhou

Cities in hilly arid areas of northwest China have generally experienced a low level of economic development; they also have unique natural characteristics such as climate, soil, terrain, environment, and surface cover. High quality ecological lands are those that provide humans and the environment with relatively high levels of ecological services including soil, water, and air purification, adsorbing pollutants, or providing water or nutrients needed by plants. In this study, ecological lands were classified as woodland, grassland, water area, and bare land. The present study constructed an ecological land model designed to evaluate the importance of such land from the perspective of ecological service function and ecological demand intensity. Results revealed that: (1) This model can help researchers to better analyze the structure and spatial characteristics of ecological land in cities and also meet the needs of ecological protection and urban management in highly urbanized areas. (2) In terms of ecological service function and ecological demand intensity, the most important ecological land is mostly distributed in densely populated and urbanized areas, and the spread of urbanization is conducive to the improvement of land ecological value for the arid hilly area of northwest China. (3) Among all types of ecological land, the water area had the highest ecological value in the study area, while the grassland had the most potential for improvement, as careful planning and use can allow grassland to function as an ecological barrier while providing good, aesthetically pleasing space for leisure activities for the general public. (4) Qilihe and Xigu districts have more generally important graded areas of forest, grassland, and bare land, although the current ecological value of these lands is limited, though they have great potential for ecological improvement.