农村多水塘系统水环境过程研究进展

Agricultural multi-pond systems and their hydrological processes: a review

农村多水塘系统由于其不可替代的水资源蓄积和营养物去除功能,广泛分布于我国东部和南部地区。在分析多水塘系统水环境过程研究进展的基础上,指出了目前多水塘系统水环境过程研究中的不足及未来发展趋势。关于多水塘系统的研究主要从两个尺度展开,分别是生态系统尺度和景观尺度。(1)基于生态系统尺度的多水塘系统水环境过程研究主要表现在两方面。首先,多水塘系统在改变区域水文情势上发挥着重大作用。多水塘系统能有效降低流速,且增加地表径流的滞留时间;其次是对多水塘系统水质的研究,主要包括水塘对污染物截留降解能力的研究、水塘底泥和水体之间营养物形态转化和输移机制的研究。(2)基于景观尺度的多水塘系统水环境过程模型研究主要包括构建经验模型和机制模型两方面。经验模型主要是利用统计分析方法分析景观格局与水环境之间关系;适用于农村多水塘系统的水环境机制模型主要包括国外的SWAT、HSPF、DRAINWAT和TOPMODEL模型。农村多水塘系统的研究可以为建设生态新农村提供科学依据。

Agricultural multi-pond systems, typical of the landscape of China, have been documented historically for 3,000 years. As small-water conservancy projects, multi-pond systems are widely distributed in southern China. They comprise a large artificial irrigation network system, composed of many tiny ponds, scattered in agricultural fields and connected by ditches and streams. They perform a key function in hydrological regulation and mass cycling. In recent decades, there have been many studies on the ecological process of muhi-pond systems. Based on the review of muhi-pond systems and their hydrological processes, the main study of multi-pond systems can be divided into two aspects： ecosystem and landscape scales. （ 1 ） For ecosystem scales, the change of hydrological processes and the nutrient recirculation were developed. Local hydrological cycling was changed, and the ponds could control flooding rate and increase terminal dwell times of runoff. However, the muhi-pond system has other ecological functions that clean up water quality, i.e., sediment and nutrient retention. （2） For landscape scales, we reviewed examples of empirical models and potential mechanistic modeling tools that could be applied to further advance scientific understanding. Statistical models allow a steady state analysis that links landscape characteristics to watershed hydrology and water quality data. However, mechanistic watershed models are structured to dynamically link landscape features to downstream hydrological and biogeochemical processes. Here we discuss a subset of watershed models readily adaptable to address multi-pond connectivity questions, including the Soil and Water Assessment Tool （SWAT）, Hydrological Simulation Program FORTRAN （HSPF） model, DRAINmod for WATershed model （DRAINWAT）, and TOPMODEL model. In watersheds with a sufficiently dense distribution of ponds, the hydrologic functions they provide could have important implications for flood regulation and mitigation of the future effects of climate and land use change. With the recognized function of multi-pond systems, the focus was on the hydrological module of ponds, and this was developed to enhance the models above. Based on the review of multi-pond systems, there were some shortages of studies between multi-ponds and their ecological process, including the following aspects. Firstly, analyses on ecological scales were based on the cycling mass in one pond and typically used field measurements to elucidate the source of a dissolved element in surface waters by accounting for all known sources, losses, or sinks. However, pond connectivity was often overlooked. In a landscape context, thousands of ponds are connected in a large network to provide ecological function at a regional scale. Secondly, several empirical methodologies hold the potential to improve the accuracy of mechanistic modeling approaches by providing parameter value estimates. Empirical methodologies, such as similar statistical approaches, could therefore highlight important factors associated with ponds （e.g., maximum and minimum volumes and surface depression storages, distance to stream network） that influence flow and highlight important variables to accurately parameterize the distributed landscape-scale mechanistic models. Thirdly, the research of multi-pond systems in China always depended on the foreign models, which cannot accurately reflect the characteristics of systems in China.