Ecohydrological Variation and Multi-Objective Ecological Water Demand of the Irtysh River Basin

Abstract

Hydrological processes regulate the ecological processes of a basin. Climate change and anthropological activities lead to changes in the natural hydrological process of rivers, whereas variations in hydrological processes can disrupt the stability of ecosystems, resulting in various ecological challenges. Quantitative evaluation of ecological water demand and its key components can play a key role in the sustainable development of ecosystems. The studies of ecohydrological variation and multi-objective ecological water demand are of great significance for ecological protection and remediation due to the unique characteristics of each river basin and diverse ecological protection objectives. This study identified ecohydrological variation in ecosystems, focusing on the Irtysh River Basin as a case study, and improved methods for ecological water demand of valley forests and grasslands in terrestrial ecosystems and for the ecological water level of lake ecosystems. The results demonstrated that: (1) a drastic decrease in the annual average river flow of the basin and significant changes in ecohydrological characteristics can lead to reduced biomass; (2) the ecological water demand of valley forests and grasslands during the critical ecological stage (April–September) was 521 million m³, with 52.4% of total demand occurring in June and July. The minimum ecological water levels of the Burultokay and Jili lakes were 478.66 m and 480.66 m, whereas the maximum levels were 482.80 m and 483.20 m, respectively; (3) ecological regulation based on catchwork irrigation technology can create hydrological processes that meet the water demands of valley forests and grasslands and achieve remediation of the terrestrial ecosystem. The ecological water levels and the ecosystem balance of the Burultokay and Jili lakes can be maintained by optimizing the replenishment flow from the Irtysh River to the Burultokay Lake under different precipitation levels. This study can act as a reference for the ecological protection and remediation of the Irtysh River Basin and similar ecosystems globally.