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River Hydrology, Flow Alteration, and Environmental Flow

Profile image of Bernhard ZeiringerBernhard Zeiringer

Riverine Ecosystem Management

https://doi.org/10.1007/978-3-319-73250-3_4
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23 pages

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Abstract

The water runs the river." This chapter focuses on the river flow as the fundamental process determining the size, shape, structure, and dynamics of riverine ecosystems. We briefly introduce hydrological regimes as key characteristics of river flow. Hydrological regimes are then linked to habitats and biotic communities. The effects of flow regulation as a result of human activities such as water abstraction (irrigation and hydropower), river channelization, land use, and climate change are demonstrated. Finally, methods to assess the environmental flow, the flow that is needed to maintain the ecological integrity, are described, and examples of successful flow restoration presented. 4.1 The Water Cycle and Hydrological Regimes In temperate zones water received via precipitation is either stored in ice and snow during winter or infiltrates into the groundwater and is released into rivers during summer. Water cycles through stages of evaporation, water storage in the atmosphere, precipitation, (sub)surface runoff, and storage in the ocean. The water cycle and climatic conditions form the boundary conditions for the hydrological regimes that define distinct seasonal and daily flow patterns. High altitude rivers receive water mainly from glacial melt during summer with distinct diurnal melting peaks following air temperature warm-up (glacial regime) (Fig. 4.1). At lower elevations snow melting in spring causes seasonal peaks (nival regime), while periods of high flow and floods due to rainfall can occur at any time of the year (pluvial regime).

Key takeaways
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  1. River flow fundamentally shapes riverine ecosystems and is crucial for maintaining ecological integrity.
  2. Human activities have appropriated over 50% of the world's accessible surface water, projected to reach 70% by 2025.
  3. Flow regulation significantly impacts aquatic biodiversity, with 60% of rivers fragmented by hydrologic alteration.
  4. Environmental flow (EF) is essential for sustaining ecosystems, requiring specific discharge characteristics for health maintenance.
  5. Assessing EF methods vary in complexity, with over 200 approaches developed to address ecological and management needs.

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Sandipan Ghosh

Sustainable Water Resources Management

Environmental flow is the minimum flow required in a fluvial system to maintain its ecological health and to promote socioeconomic sustainability. The present work critically examines the concept of the environmental flow in the context of dams and development using a systematic methodology to find out the previous works published during the last 3 decades (1990-2020) in different search engines and websites. The study reviews that structural interventions in the form of dams, barrages, weirs, etc. impede the natural flow of the rivers. Moreover, other forms of development such as industrialization, urbanization, and expansion of modern agriculture also exacerbate the problems of environmental flow across the world, especially in monsoon Asia. The present case of the environmental flow for the Damodar River portrays that the construction of dams and barrages under the Damodar Valley Project have significantly altered the flow duration, flood frequency, and magnitude (high-frequency low magnitude events in the post-dam period), while urban-industrial growth in the basin has polluted the river water (e.g., lower dissolved oxygen and higher biological oxygen demand). This typical alteration in the flow characteristics and water quality has threatened aquatic organisms, especially fish diversity and community structure. This review will make the readers aware of the long-term result of dam-induced fluvial metamorphosis in the environment through the assessment of environmental flow, species diversity, flow fluctuation, and river pollution. The study may be useful for policy-making for ushering in the sustainable development pattern that will attract future researchers, planners, and stakeholders.

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Damming reduced the functional richness and caused the shift to a new functional state of the phytoplankton in a subtropical region
Yasmin Souza

Hydrobiologia, 2020

contains supplementary material, which is available to authorized users.

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Environmental Flow Assessment Using Low-flow Index Method in Upper Citarum River Basin, West Java, Indonesia
Indratmo Soekarno

The Open Civil Engineering Journal, 2022

This research aimed to determine the amount of environmental flow (EF) required to sustain the river's function in supporting ecological balance.

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The natural flow regime: A master variable for maintaining river ecosystem health
Dr. JAGDISH CHANDRA Kuniyal

Ecohydrology, 2020

River health is sustained by time‐based variation in their flows, and the maintenance of natural flow regime is essential for keeping the rivers healthy. However, the dynamism in natural flow regime now stands altered by changing climate, and the omnipresent regulation of river flows throughout the world has severely impacted the river health. It is well documented that harnessing and altering the flow of the rivers and streams comes at a huge cost. Numerous rivers in the world have stopped supporting socially and economically important native species or sustain vibrant ecosystems that offer valuable goods and services. The alteration of the natural flow regime has led to the collapse of many healthy and resilient river ecosystems throughout the world. Therefore, to ensure appropriate naturalized flow regimes for riverine organisms and a sustainable nexus between energy demand, water requirements and climate, more understanding is required to study the consequences of alteration in ...

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