Abstract
Human-controlled reservoirs have a large influence on the global water cycle. While global hydrological models use generic parametrisations to model human dam operations, the representation of reservoir regulation is often still lacking in Earth System Models. Here we implement and evaluate a widely used reservoir parametrisation in the global river routing model mizuRoute, which operates on a vector-based river network resolving individual lakes and reservoirs, and which is currently being coupled to an Earth System Model. We develop an approach to determine the downstream area over which to aggregate irrigation water demand per reservoir. The implementation of managed reservoirs is evaluated by comparing to simulations ignoring inland waters, and simulations with reservoirs represented as natural lakes, using (i) local simulations for 26 individual reservoirs driven by observed inflows, and (ii) global-scale simulations driven by runoff from the Community Land Model. The local simulations show a clear added value of the reservoir parametrisation, especially for simulating storage for large reservoirs with a multi-year storage capacity. In the global-scale application, the implementation of reservoirs shows an improvement in outflow and storage compared to the no-reservoir simulation, but compared to the natural lake parametrisation, an overall similar performance is found. This lack of impact could be attributed to biases in simulated river discharge, mainly originating from biases in simulated runoff from the Community Land Model. Finally, the comparison of modelled monthly streamflow indices against observations highlights that the inclusion of dam operations improves the streamflow simulation compared to ignoring lakes and reservoirs. This study overall underlines the need to further develop and test water management parametrisations, as well as to improve runoff simulations for advancing the representation of anthropogenic interference with the terrestrial water cycle in Earth System Models.
Highlights
The implementation of managed reservoirs is evaluated by comparing to simulations ignoring inland waters, and simulations with reservoirs represented as natural lakes, using (i) local simulations for 26 individual reservoirs driven by observed inflows, and (ii) global-scale simulations driven by runoff from the Community Land Model
In contrast to previous studies, we evaluate the implementation of the Hanasaki et al (2006) parametrisation in a global river routing model that operates on a vector-based river network, mizuRoute
The maximum storage capacity is provided by Global Reservoir and Dam dataset (GRanD) for all reservoirs on the river network, and these systematic storage biases may be caused by discrepancies between the real reservoir capacity and those reported in GRanD
Summary
The terrestrial global water cycle is fundamentally altered by human activities like groundwater pumping, river water ab straction for irrigation and the construction of large dams (Oki and Kanae, 2006; Rockström et al, 2009; Wada et al, 2014). In MIROC-INTEG-LAND, water management modules have recently been incorporated in the land component of the MIROC Earth System Model, together with crop production, land ecosystem and land use modules (Yokohata et al, 2020) These developments overall suggest that reservoir management could potentially be considered in upcoming rounds of the Coupled Model Intercomparison Project (CMIP; Eyring et al, 2016) or other multi-model assessments. 90 Natural lakes and reservoirs are integrated in the vector-based river network as hydrological features with additional parameters including information on the characteristics of the lake and/or reservoir, like maximum capacity (Gharari et al, in prep.) This approach allows to model the lake and reservoir water balance, using data on precipitation and evaporation from the water surface, in combination with parametrisations providing information on the releases, both natural outflows and regulated discharge. The IRF routing scheme was used for river channel routing that produces the discharge into lakes and 95 reservoirs
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
