基于InVEST模型的疏勒河上游产水量时空变化特征分析

开展山区流域产水量的定量评估研究,有利于区域水资源保护规划的制定、生态补偿机制的建立以及生态平衡的维系。然而,目前对我国西部高寒山区产水量的时空变化评估及其影响因素的研究依然较为缺乏。选取青藏高原东北缘祁连山西段疏勒河上游为研究区,基于InVEST(Integrate Valuation of Ecosystem Services and Tradeoffs Tools)模型定量估算并分析了2001-2019年产水量的时空变化特征及影响因素。结果表明:(1)2001-2019年,研究区年均气温和年实际蒸散量呈增加趋势(P>0.05),年降水量和NDVI则显著增加(P<0.05);(2)年均总产水量为13.66×10⁸ m³,空间分布呈现山地高海拔区较高,河谷低海拔区较低的特征;(3)19年来产水量以0.26×10⁸ m³/a的速率显著增加(P<0.01)。其中,高海拔区的产水量显著增加,约占整个研究区的32.01%;然而,仅有8.39%的低海拔区产水量显著下降(P<0.05)且集中分布在西北部;(4)产水量与降水量显著正相关,同气温、实际蒸散量、归一化植被指数(NDVI, Normalized Difference Vegetation Index)和根系深度显著负相关(P<0.001);(5)产水功能一般重要级别区占研究区面积的47.26%,极重要和高度重要级别区占总面积的28.25%。研究为祁连山国家公园水资源的动态评估、有效管理和可持续发展提供了科学参考。

Spatiotemporal variation of water yield in the upstream regions of the Shule River Basin using the InVEST Model

Ecosystem service function refers to the natural environmental conditions and utilities that the ecosystem forms and maintains to promote human survival and development. Many ecosystem service functions are of great importance to human wellbeing, especially those related to water. Water yield is a key index characterizing the regulation function of ecosystem in watershed and plays a critical role in the sustainable development of these sectors, including agriculture, industry, fisheries, and domestic activities, as well as directly impacts the regional economy and society. Climate and land use changes are the main factors affecting the spatiotemporal variation of water yield. In the context of global climate change, the quantitative assessment of water yield makes significant sense on formulating the water resource protection planning, establishing the ecological compensation mechanism and maintaining the ecological balance in the watershed. However, little research has been conducted on the spatiotemporal variation of water yield and its influencing factors in the alpine region of western China. The Shule River Basin, located in the northeastern margin of the Qinghai-Tibet Plateau and the western part of the Qilian Mountain, is the "Lifeline" and "Natural Water Tower" of farmers and herdsmen in the Hexi Corridor region of Northwestern China. This study, using the upstream regions of the Shule River Basin as the study area, evaluated the spatiotemporal variation of water yield in 2001-2019 based on Integrate Valuation of Ecosystem Services and Tradeoffs Tools (InVEST) model and examined the relation between the water yield and influential environmental factors using correlation analysis. To evaluate the performance of the InVEST model, we analyzed the relationship between the simulated total water yield and measured total water yield. It showed that the InVEST model had a good performance in estimating water yield (R²=0.986, P<0.05) for alpine region. The results demonstrated that: (1) the mean annual temperature and annual actual evapotranspiration showed an increasing trend (P>0.05), while annual precipitation and Normalized Difference Vegetation Index (NDVI) increased significantly (P<0.05) in 2001-2019. (2) The mean annual total water yield was 13.66×10⁸ m³, and the water yield was higher at the mountainous high-altitude regions and lower at the low-altitude regions of river valley. (3) The water yield significantly increased with a rate of 0.26×10⁸ m³/a from 2001 to 2019 (P<0.05), and the water yield significantly increased in the high-altitude regions (accounting for 32.01%), while the low altitude regions of the northwest significantly decreased and accounted for only 8.39% (P<0.05). (4) There were significantly positive correlations between water yield and precipitation, and negative correlations between water yield and air temperature, actual evapotranspiration, NDVI and root depth (P<0.001). (5) The water yield function of the generally important area which refers to poor water yield function had a proportion of 47.26%, whereas the very important region accounted for 28.25% of the total area. The results can provide scientific insights for dynamic assessment, effective management, and sustainable development of water resources in the Qilian Mountain National Park of China.