基于SWAT模型的森林分布不连续流域水源涵养量多时间尺度分析

为解决森林分布不连续流域森林水源涵养功能及其多时间尺度特征的定量评价问题,根据分布式水文模型（SWAT）的特点,提出了反映森林斑块空间分布的水文响应单元划分方法,以及基于水量平衡法的森林不连续分布流域森林水源涵养量计算公式。以东南沿海的晋江流域为例,构建了2006年土地利用条件下的日时间步长SWAT模型,统计分析了2002—2010年降水条件下森林水源涵养量的时空变化规律。结果表明：① 构建的晋江流域SWAT模型精度较高,面积阈值为零生成的水文响应单元比较准确地反映流域森林斑块分布,提出的森林水源涵养量计算公式适用于森林空间分布不连续流域森林水源涵养量的多时间尺度分析,为流域森林水源涵养功能评价提供了一个新的方法。② 晋江流域森林水源年涵养量271.41~565.25 mm;月涵养量-29.15~154.59 mm;日尺度的极端降水期皆为正值,极端枯水期都为负值。表明年际之间不存在森林水源涵养的蓄丰补枯调节作用,但在年内的部分月份得到体现,而日尺度的森林蓄丰补枯功能充分发挥。从而揭示了不同时间尺度森林水源涵养量及其蓄丰补枯功能的差异。

Multi-time scale analysis of water conservation in a discontinuous forest watershed based on SWAT model

A method has been developed based on the Soil and Water Assessment Tool (SWAT) to quantitatively evaluate the water conservation function of forests and its multi-time scale characteristics in a discontinuous forest watershed. Using this method, we have divided hydrological response units (HRU) based on the spatial distribution of forests, and derived a formula to quantify the water conservation in discontinuous forest watershed based on the water balance method. Here we take the Jinjiang River Basin in southeast coastal China as an example. We constructed SWAT model under land use conditions in 2006 and analyzed the temporal variation of forest water conservation in the study river basin under precipitation conditions from 2002 to 2010. The results show that (1) the SWAT model of the study area is of high accuracy, and the hydrological response unit can accurately reflect the distribution of forest patches when the area threshold is zero. The model provides a new method for evaluation of forest water conservation function in the discontinuous forest watershed using a distributed hydrological model. (2) The annual conservation of forest water in the Jinjiang River Basin was 271.41-565.25 mm. The annual conservation function of forest water is relatively stable, and there was no runoff regulation between consecutive years. The monthly conservation ranged from -29.15 mm to 154.59 mm, which is positive for most months of the year. The forest water conservation was positive in extreme precipitation period, and negative in extremely dry period. This demonstrates the function of forest water conservation in retaining rainwater in wet periods to decrease flood in the river and supplying water in dry periods to supplement the flow at the daily scale was more effective than that at the monthly scale.