Invertebrate response to impacts of water diversion and flow regulation in high‐altitude tropical streams

Abstract

Water supply systems are critical infrastructure that provides food and energy security for developed societies. The operation of reservoirs (flow regulation) and water intakes (water diversion) has known negative impacts on aquatic ecosystems; however, quantification of ecological impacts and examination of these two types of flow alteration remain a developing area of research. We investigated the individual and combined impact of flow regulation and water diversion on stream ecosystem integrity, the freshwater macroinvertebrate community, and the population structure of flow-sensitive insects. For 2 years, we monitored quarterly discharge, physical and chemical stream conditions, and benthic invertebrates of four high-altitude tropical streams that are part of the water supply system of Quito, Ecuador. Flow regulation caused a loss of the hydrological seasonality of these streams, including a decrease in stream depth and biotic quality. Water diversion caused a decrease in dissolved oxygen and overall ecosystem integrity. Freshwater invertebrate density and richness decreased as a result of water diversion and flow regulation. The combined flow alteration in these streams decreased the density of nymphal stages of the widely distributed mayfly Andesiops peruvianus. Given the societal needs for food and energy security, water management for diversion (e.g., irrigation) and in-line storage practices (e.g., hydroelectric dams) are anticipated to increase. This research suggests that the negative environmental impacts of flow alteration could be mitigated with discharge releases designed to approximate the natural hydrologic regime of undisturbed streams. K E Y W O R D Sdomestic water use, flow alteration, invertebrates, páramo

Impacts of streamflow alteration on benthic macroinvertebrates by mini-hydro diversion in Sri Lanka

“…Hydropower exploitation frequently induces reduction in streamflow magnitude, which is a strong predictor of biological integrity 41 . However, the impact on aquatic communities is expected to be lower in case of run-of-the-river schemes 18,19 and minor intakes [20][21][22] than in case of reservoirs [14][15][16] . In the latter case, more severe reductions of the flow variability and changes of flow timing add to the substantial decrease of the flow magnitude.…”

“…Biological responses to flow alterations thus strictly depend on the context but also vary according to the kind of off-stream diversion scheme. To date, much of the research has been conducted on dams and impoundments 14 – 17 , mainly of large size, and few studies have assessed the ecological effects of run-of-the-river schemes 18 , 19 and minor intakes 20 – 22 .…”

Response of benthic macroinvertebrates to different hydropower off‐stream diversion schemes

“…Robust flow–ecology relationships are recognized as the basis to setting up adequate e‐flows (Ramos et al, 2018; Rosero‐López, Knighton, Lloret, & Encalada, 2019; Warfe et al, 2014; Wu et al, 2020). Numerous studies are available focusing on the structure of these relations (revised, e.g., in Gillespie, Brown, & Kay, 2015; Poff & Zimmerman, 2010), their intrinsic complexity and the related needs to perform monitoring and adaptive management to verify that e‐flows can provide the required outcomes (Harwood et al, 2018; McManamay, Brewer, et al, 2016).…”

Effects of experimental warming on two tropical Andean aquatic insects

“…Records of daily air temperatures in this area fluctuate from 5°C to 17°C, and precipitation is lowest from September to February [ 70 ]. The annual average temperature in streams from the Chalpi Grande watershed was 8.14°C (SD = 0.65) [ 71 ]. On the day of insect collection, the stream temperature was 9.9°C, oxygen saturation was 90.3%, and dissolved oxygen was 6.9 mg/L.…”