Abstract
We investigated how hydro-climatological changes would affect fluvial forces and inundated area during a typical high-flow situation (MHQ, mean high discharge), and how adaptive regulation could attenuate the climate change impacts in a low-relief river of the Southern Boreal climate area. We used hydrologically modeled data as input for 2D hydraulic modeling. Our results show that, even though the MHQ will increase in the future (2050–2079), the erosional power of the flow will decrease on the study area. This can be attributed to the change of timing in floods from spring to autumn and winter, when the sea levels during flood peaks is higher, causing backwater effect. Even though the mean depth will not increase notably (from 1.14 m to 1.25 m) during MHQ, compared to the control period (1985–2014), the inundated area will expand by 15% due to the flat terrain. The increase in flooding may be restrained by adaptive regulations: strategies favoring ecologically sustainable and recreationally desirable lake water levels were modeled. The demands of environment, society, and hydropower are not necessarily contradictory in terms of climate change adaptation, and regulation could provide an adaptive practice in the areas of increased flooding.
Highlights
Two third of the world’s fresh water flowing into the oceans is obstructed by dams [1,2,3]
If the current regulation rules are used in the future, the mean high discharge will increase 8% from the control period as a consequence of climate change (Table 3)
We investigated how the predicted hydro-climatological changes will affect the distribution of fluvial forces and inundated area during typical high-flow situation (MHQ, mean high discharge), and how modifying the regulation standards could alter the climate change impacts in a low-relief river of the Southern Boreal climate area, Southwestern Finland
Summary
Two third of the world’s fresh water flowing into the oceans is obstructed by dams [1,2,3]. Regulation causes less variable flows in the rivers downstream and increasing fluctuation of water levels in the reservoirs behind the dams [2,4]. The water volume increase upstream of a dam may cause inundation of terrestrial and riparian areas, affecting the riparian ecosystems [2,9,13]. Downstream of a dam, the flood peaks and the frequency of overbank flooding as well as the groundwater formation are reduced [3]. This may hinder channel development, and reduce geomorphologic and floodplain productivity [13]. In the Southern Boreal climate area, flow regulation may increase winter stream flow and temperatures, reduce ice formation and surface ice cover downstream of power plant [14], and thereby increase ice dam formation probability [5,15]
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