Water Resources Research Act Program

Details for Project ID 2018MT324B

Deciphering the combined effects of artificial and natural water storage structures on late-season flows

Institute: Montana
Year Established: 2018 Start Date: 2018-03-01 End Date: 2020-02-28
Total Federal Funds: $14,998 Total Non-Federal Funds: $39,774

Principal Investigators: Hongyi Li

Project Summary: The damaging droughts have been significantly reducing the late-season flows in Montana’s headwater, and will likely be even more severe in the next few decades. Natural water storage has been proposed and currently under implementation as a solution to mitigate the water stress caused by droughts. However, it remains a challenge how to scale up these natural storage innovations and their impacts from the current pilot projects to the basin scale, e.g., the whole Jefferson River Basin, while accounting for the effects of artificial reservoirs. The combined effects of natural water storage and reservoir at the basin-scale should be understood from a river network standpoint. Both natural water storage and reservoirs are functioning to store excess river water during the high flow and low demand periods, then release water back to river channels when it is more needed. They thus both affect the late-season flows, however, in very different ways: 1) the individual natural water storage is usually much smaller than a reservoir storage, hence likely less effects on streamflow; 2) natural water storage is more closely interacting with the shallow groundwater storage and more likely to interact with deep groundwater storage (e.g., regional groundwater system in the confined aquifer); 3) natural water storage is economically much cheaper to develop than a reservoir, hence more feasible to have a large number of natural water storage structures in a basin; 4) once built, natural water storage structures require less maintenance and management than reservoirs, whilst the latter are more dynamically subject to the water-related policies and regulations. With the endorsement from The Nature Conservancy, we propose to develop a basin-scale hydrological modeling framework to integrate the hydrological effects of the natural storage, groundwater storage, channel storage and reservoirs, and more importantly, their interactions. The integrated basin-scale hydrological model will be built on top of the Tsinghua Hydrological Model based on the Representative Elementary Watershed approach that has been jointly developed, maintained and well published by several hydrology groups, including PI Li’s. THREW utilizes the digital topography data to discretize the study domain into a number of Representative Elementary Watersheds (REWs), which are linked together by the river network. In this proposed research, the natural water storage structure will be represented as a sub-zone in a REW adjacent to the main channel and/or sub-stream network, and any existing reservoir will be represented a sub-zone which is physically located on the main channel. The proposed basin-scale modeling framework will help assess the cumulative effects of natural water storage in a more rigorous way under various climate change and reservoir management scenarios. It will also shed lights on the coordinated managements between the existing and planned natural water storage structures and existing reservoirs. We therefore hope that the proposed research will help to identify the most efficient way to plan and implement natural water storage at the whole basin level, so that the optimum increase in late-season flows could be achieved in coordination with the improved management of existing reservoirs.