Hydrological alteration and biodiversity change along the river network caused by anthropogenic activities and climate variability

Abstract

Background Population growth and intensified human activities in conjunction with climate variability continue to affect the hydrologic cycle, aquatic and terrestrial flora and fauna. In this regard, understanding interactions among ecosystem functions, impacts of anthropogenic interventions and those of climate variability is vital for projecting future ecosystem responses to human activities and climate forcing. The objectives of this study are to determine the ecological flow state via eco-flow index based on discharge hydrograph, to model the ecological diversity through the Shannon diversity index, and to assess the degree of hydrologic alteration using indicators of hydrologic alteration and range of variability approach in six hydrometric stations along the Zayandeh-Rud River in central Iran. The river drains into Gavkhuni Marsh. Also, the streamflow-induced potential changes for Capoeta damascina (a cyprinid fish species of the genus Capoeta), Petroleuciscus esfahani (a small cyprinid fish) and Aphanius isfahanensis (a Cyprinodontid fish) are evaluated. The outcome is expected to assist managers with understanding the effects of anthropogenic activities and climate variability on Gavkhuni aquatic ecosystems so that management options that enhance species resilience and adaptability are outlined. Results Human activities, a primary factor influencing the natural flow regime, caused a significant increase in the minimum flow, July to March streamflow, low pulse number, and the number of reversals in most studied stations. On the contrary, some other hydrologic indices declined in value. Reservoir impoundment, the most prominent factor among human interventions, resulted in an overall alteration degree of 74.8% in streamflow. Climate variability impacted the natural flow regime in the range of low degree hydrologic alteration (27.3%). In addition, the biodiversity of the study basin, as modeled by the Shannon diversity index, had strong relevance to the annual eco-surplus and was more sensitive to summer floods and autumn hydrological droughts than other factors. Conclusions This study corroborates the effectiveness of scenario-based hydrological modeling framework in evaluating the impacts of climate variability and human activities imposed on natural flow metrics. Additionally, the recently introduced eco-flow metrics based on discharge hydrographs and the Shannon diversity index based on indicators of hydrological alteration may be adopted in basins lacking ecological data. These two indices can effectively identify the most prominent factors in hydrological alteration and biodiversity change through a river network and may provide scientific decision-making support for water resource management in the study area.

Using Game Theory Algorithm to Identify Critical Watersheds based on Environmental Flow Components and Hydrological Indicators

“…Ely et al, 2020;Villablanca et al, 2022;Yan et al, 2010;Zolfagharpour et al, 2022). In PRGS watershed, which was affected by Yamchi dam, N-zero index in the pre-dam period was 0.033, but in the post-dam period, it increased to 82.11.…”

Future climate impacts on biodiversity trends in major global rivers

“…River biodiversity is strongly associated with hydrological characteristics and its temporal dynamics could be projected based on eco-hydrological parameters, which can be monitored in high frequency and requires less manpower compared to directly monitoring species. For example, Shannon index (SI) based on eco-hydrological parameters has been suggested as a proxy for assessing biodiversity trends in river ecosystems 10,11,12 . Such an approach also represents a promising tool to assess the effects of climate change-induced ow alteration on river biodiversity, which has received increasing attention from scholars worldwide 2,13,14 .…”

Impact of interbasin transfer hydroelectric project on downstream aquatic habitat

“…Several methodologies were developed in the past few decades to understand the hydrologic alterations. Richter et al (1996) developed an approach termed Indicators of Hydrologic Alteration (IHA), composed of 33 hydrologic parameters categorized into five groups that are sensitive to the anthropogenic activities of the riverine ecosystem (Ely et al, 2020; Gao et al, 2020; Marak et al, 2020; Zolfagharpour et al, 2022). A longer dataset is crucial for accurate analysis through IHA.…”