Flow alteration signatures of diversion hydropower: An analysis of 32 rivers in southwestern China

Abstract

Hydrologic changes caused by diversion hydropower are poorly described. Herein, we evaluate hydrologic alteration in 32 ungauged rivers developed for diversion hydropower. We simulated long-term unregulated discharge records before perturbing flows with the hydropower diversion and comparing periods with and without diversion. We detected statistically significant changes to flow regime metrics across all rivers. Magnitudes across a range of flows consistently decreased following diversion, flow variability decreased substantially, and transitions between flows of different magnitudes became more abrupt. Magnitudes of 7-day minimum flows were lower by a mean of 41 ± 23% (p < .05 for 19 rivers), annual maximum flows decreased significantly (p < .05) in 22 rivers, and 7-day maximum flows decreased by a mean of 52 ± 18% (p < .05 for 26 rivers). Temporally dynamic low to moderate flows were replaced by static minimal flows, leading to a mean 184 ± 49% increase in flow constancy. Mean duration of events sustained below the prediversion Q 75 increased (p < .05 for 32 rivers) from a mean of 3 days to a mean of 27 days after diversion. Mean hydrograph rise and fall rates doubled and tripled, respectively (p < .05 for 28 rivers). We detected few changes to peak flow timing. Although direction of observed change was consistent among the rivers, magnitudes and significance of response often varied between rivers. A proposed diversion index largely explained response variability among the 32 rivers. Results highlight that hydropower systems without storage reservoirs can profoundly affect river flow regimes when water is diverted from the river.

Water quality impacts of small hydroelectric power plants in a tributary to the Pantanal floodplain, Brazil

“…Another caveat is that our study does not examine a long cascade of SHPs like those that exist in many parts of the world. Effects that are too small to detect across one or a few SHPs can become important cumulative changes as more SHPs are built (Kibler & Alipour, 2017). Dewatering of the natural river channel by SHP diversion channels is likely to be ecologically significant, although complete dewatering as has been reported in China is less likely here; in Mato Grosso State, dam operators are required to maintain approximately 10% of the mean monthly discharge in the natural channel as “ecological flow.”…”

Long-Term Downstream Effects of a Dam on a Lowland River Flow Regime: Case Study of the Upper Narew

“…Reporting downstream effects of the SR on the flow regime of the Narew River, and considering a number of environmental issues examined in the Narew Valley in recent years, similarly to Romanowicz and Osuch [28] we stress that further research is critically needed to reveal the influence of the SR-induced flow regime change on biota and biocoenosis of this area in a site-specific context. Based on the knowledge of the response of riparian environments to reservoir-influenced flow regime changes [1,3,4,6,7,50,51], we stress that keeping the status quo with respect to the regulation of river discharge by the SR can eventually result in irreversible changes of the downstream environment of the Narew River and its valley, such as the deterioration of the main objects of environmental conservation of the NNP related to a functioning anastomosing river channel. Considering the results of Piniewski et al [52], and given the findings presented in this paper, we also stress that the SR-induced flow regime changes of Narew are likely to be more unilateral and stronger than the ones resulting from prospective climatic changes.…”

“…The influence of dams on river systems is reportedly several times greater than, for example, the influence of climate change [2]; therefore, the analysis of downstream effects of dams (reservoirs) remains an important issue in international scientific literature [3][4][5]. Based on the modification of river discharge on an hourly and daily basis, seasonal changes of flow regimes [6,7], and water temperature modification [8] in impounded rivers, dams can be considered a key element affecting the hydrology of downstream reaches of rivers.…”

Effects of small hydropower plants in cascade arrangement on the discharge cyclic patterns

“…An additional aspect of the outlined problem is that most low head dam studies comprise a single facility, hence ignoring potential cumulative disturbances when a set of small hydropower plants are placed in a cascade (FENCL et al, 2015;KIBLER;ALIPOUR, 2014). Nonetheless, for taking utmost advantage of the hydropower generation potential of a river, SHPs are frequently allocated in such an arrangement.…”