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 Q75 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.

Publication Date

2-10-2017

Number of Pages

14

Document Type

Paper

Language

English

Source Title

Ecohydrology

Volume

10

Issue

5

College

College of Engineering and Computer Science

ISSN

1936-0592

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