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Related Concept Videos

Plane Potential Flows01:23

Plane Potential Flows

Plane potential flows simplify fluid motion by assuming the fluid to be irrotational and incompressible. These characteristics allow these flows to be described by a velocity potential function, ϕ, representing the flow speed in a given direction, and a stream function, ψ, that visualizes the flow path, both governed by Laplace's equation. These parameters help in estimating flow patterns, velocity distributions, and pressure fields around various hydraulic structures.
Uniform Flow
Uniform flow...
Gradually Varying Flow01:29

Gradually Varying Flow

Gradually varying flow (GVF) in open channels describes situations where water depth changes slowly along the channel due to factors like non-uniform bed slope, channel shape variations, or obstructions. This flow type occurs when the depth adjusts gradually to balance gravitational forces, shear forces, and energy requirements, resulting in a low rate of depth change.Characteristics of Gradually Varying FlowGVF is commonly observed in natural streams, rivers, and canals, where flow depth...
Rapidly Varying Flow01:24

Rapidly Varying Flow

Rapidly varying flow (RVF) in open channels is characterized by abrupt changes in flow depth over a short distance, with the rate of depth change relative to distance often approaching unity. These flows are inherently complex due to their transient and multi-dimensional nature, making exact analysis difficult. However, approximate solutions using simplified models provide valuable insights into their behavior.Key Features of Rapidly Varying FlowRVF is commonly observed in scenarios involving...
Plotting of Topographic Maps01:29

Plotting of Topographic Maps

Topographic maps represent the Earth's surface features using contour lines, which connect points of equal elevation to create a two-dimensional representation of three-dimensional terrain. Creating a topographic map requires a systematic approach.Begin by plotting a scaled grid and marking intersections corresponding to the survey's elevation data points. Assign elevation values at these intersections to build the base map. Next, determine contour levels using a consistent contour interval,...
Design Example: Analyzing Capacity Contours for Flood Risk Assessment01:17

Design Example: Analyzing Capacity Contours for Flood Risk Assessment

Flood risk assessment involves careful planning and analysis to ensure the safety of communities near water retention structures. Capacity contours are a vital tool in this process, as they illustrate the potential spread of water at specific levels in a given area. In the context of building a bund across a small valley, these contours play a critical role in evaluating the safety of nearby residential areas.In this example, the bund is intended to store stormwater in the valley. The engineers...
Vector Forms of Green’s Theorem01:26

Vector Forms of Green’s Theorem

The study of fluid motion often involves understanding how local rotational behavior relates to global circulation. In the context of a pond with pollutants, direct measurement of water movement along an irregular shoreline can be impractical. Green’s Theorem in vector form provides an alternative by relating the circulation around a closed boundary to properties of the flow within the enclosed region.Measurements of water velocity at different points define a continuous vector field that...

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Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation
09:49

Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation

Published on: November 18, 2015

Mapping the world's free-flowing rivers.

G Grill1, B Lehner2, M Thieme3

  • 1Department of Geography, McGill University, Montreal, Québec, Canada. guenther.grill@mail.mcgill.ca.

Nature
|May 10, 2019
PubMed
Summary
This summary is machine-generated.

Globally, only 37% of long rivers remain free-flowing, with infrastructure development fragmenting vital river ecosystems. This study maps remaining free-flowing rivers (FFRs) to aid conservation efforts.

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Area of Science:

  • Ecology
  • Hydrology
  • Conservation Science

Background:

  • Free-flowing rivers (FFRs) are critical global ecosystems supporting biodiversity and providing essential services.
  • Infrastructure development, particularly dams, poses a significant threat to river connectivity, ecosystem processes, and biodiversity.

Purpose of the Study:

  • To assess the global connectivity status of rivers and identify remaining free-flowing rivers (FFRs).
  • To provide a foundation for global and national strategies aimed at maintaining or restoring river connectivity.

Main Methods:

  • A novel method was applied to quantify riverine connectivity across 12 million kilometers of rivers globally.
  • Mapping identified FFRs and assessed their uninterrupted flow to the ocean.

Main Results:

  • Only 37% of rivers longer than 1,000 km remain free-flowing throughout their entire length.
  • A mere 23% of these rivers flow uninterrupted to the ocean.
  • Remaining FFRs are predominantly located in remote Arctic, Amazon, and Congo basin regions, with few exceptions in populated areas.

Conclusions:

  • Dams and reservoirs are the primary drivers of river fragmentation and loss of connectivity.
  • Urgent global and national strategies are needed to maintain and restore free-flowing rivers and their associated ecosystems.