Exploring the multiscale hydrologic regulation of multipond systems in a humid agricultural catchment. (1st October 2020)

• Record Type: Journal Article
• Authors: Chen, Wenjun; Nover, Daniel; Yen, Haw; Xia, Yongqiu; He, Bin; Sun, Wei; Viers, Joshua
• Is Part Of: Water research. Volume 184(2020)
• Publication Date: 2020-10-01
• Subjects: Hydrologic regulation -- Small -- Scattered wetlands -- Multipond systems -- Cascading fill-spill relationships -- Soil and water assessment tool -- Rule-based artificial intelligence; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2020.115987
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: Assessing the hydrologic processes over scales ranging from single wetland to regional is critical to understand the hydrologically-driven ecosystem services especially nutrient buffering of wetlands. Here, we present a novel approach to quantify the multiscale hydrologic regulation of multipond systems (MPSs), a common type of small, scattered wetland in humid agricultural regions, because previous studies have stopped in commending the catchment scale flood and drought resilience of these waters, and contemporary models do not adequately represent the corresponding intra-catchment fill-spill relationships. A new version of Soil and Water Assessment Tool (SWAT) was developed to incorporate improved representation of: (1) perennial or intermittent spillage connections of pond-to-pond and pond-to-stream, and (2) bidirectional exchange between pond surface water and shallow groundwater. We present SWAT-MPS, which adopts rule-based artificial intelligence to model the possibilities of different spillage directions and GA-based parameter optimization over the two simulation years (June 2017 to May 2019), with successfully replicated streamflow and pond water-level variations in a 4.8 km 2 test catchment, southern China. Water balance analysis and scenario simulations were then executed to assess the hydrologic regulation at single pond, single MPS, and entire catchment scales. Results revealed (1) the presence of 9 series- or series-parallel connected MPSs, in which pond overflow accounted for as much as 59% of the catchment water yield; (2) seasonally- and MPS-independent baseflow support and quickflow attenuation, with ranked level of pond water storage for baseflow support across different landuse types: forest > farm > village, and inversed correlation of pond spillage to baseflow and quickflow variations in the farmland; and (3) MPS-aggregated catchment flood peak reduction (>20%) and baseflow increment (26%) in the following dry days. Meteorological data analysis and simulated average daily values indicated these hydrologic patterns are credible even if extending to a 5-year period. As a first modelling attempt to explore the intra-catchment details of MPSs, our study underscores the water storage and connectivity in their hydrologic regulation, and suggests inventories, long-term field monitoring, and several research directions of the new model for integrated pond management in watersheds and river basins. These findings can inform refined assessment of similar small, scattered wetlands elsewhere, where restoration efforts are required. Highlights: Multiscale hydrologic regulation of multipond systems was assessed for the 1st time. SWAT was enhanced for cascading fill-spill relationships and groundwater exchange. Pond connections were solved with overflow representing 59% of catchment water yield. Seasonally & MPS independent baseflow support and quickflow attenuation was revealed. Water storage & spillage connections are both crucial for pond conservation efforts.