Water Resources Lecture 4
description
Transcript of Water Resources Lecture 4
![Page 1: Water Resources Lecture 4](https://reader035.fdocuments.us/reader035/viewer/2022081503/56815d7e550346895dcb8ac7/html5/thumbnails/1.jpg)
Water ResourcesLecture 4
The River Environment (2)
![Page 2: Water Resources Lecture 4](https://reader035.fdocuments.us/reader035/viewer/2022081503/56815d7e550346895dcb8ac7/html5/thumbnails/2.jpg)
![Page 3: Water Resources Lecture 4](https://reader035.fdocuments.us/reader035/viewer/2022081503/56815d7e550346895dcb8ac7/html5/thumbnails/3.jpg)
Problems with generic zoning of a river:
• Many rivers are different – they occur in different geological and climatic regions.
• Different rivers have different transitions along their profiles.
• Rivers do not often undergo a gradual transition along their profile:– What about rejuvination at a nick-point?– What happens when a tributary with very different
characteristics joins the main stream?– What happens when a river is dammed along its course?
![Page 4: Water Resources Lecture 4](https://reader035.fdocuments.us/reader035/viewer/2022081503/56815d7e550346895dcb8ac7/html5/thumbnails/4.jpg)
Hiererarchical Classification of River Systems
• Proposed by Frissel et al, 1986.• Adapted to a geomorphological classification for
Southern Africa by Rowntree and Wadeson, 1999. • Basic Principle:
– River System– River Zones– Segments– Reaches– Morphological Units– Hydraulic Biotopes
![Page 5: Water Resources Lecture 4](https://reader035.fdocuments.us/reader035/viewer/2022081503/56815d7e550346895dcb8ac7/html5/thumbnails/5.jpg)
Frissel et al
![Page 6: Water Resources Lecture 4](https://reader035.fdocuments.us/reader035/viewer/2022081503/56815d7e550346895dcb8ac7/html5/thumbnails/6.jpg)
Definitions (Frissel)
• Stream System:– All surface waters in a Watershed (catchment).
• Segment System:– Portion of a stream system flowing through a
single bedrock type, and bounded by tributary junctions or major waterfalls.
![Page 7: Water Resources Lecture 4](https://reader035.fdocuments.us/reader035/viewer/2022081503/56815d7e550346895dcb8ac7/html5/thumbnails/7.jpg)
Definitions: Frissel
• Reach System:– A length of stream segment lying between
breaks in a channel slope, local side-slopes, valley floor width, riparian vegetation, and bank material.
• Pool or riffle system:– A subsystem of a reach having characteristic
bed topography, water surface, slope, depth and velocity patterns
![Page 8: Water Resources Lecture 4](https://reader035.fdocuments.us/reader035/viewer/2022081503/56815d7e550346895dcb8ac7/html5/thumbnails/8.jpg)
Classification of Rowntree and Wadeson
![Page 9: Water Resources Lecture 4](https://reader035.fdocuments.us/reader035/viewer/2022081503/56815d7e550346895dcb8ac7/html5/thumbnails/9.jpg)
Hydraulic Biotopes
• A mosaic of small patches of uniform condition within the wetted perimeter of a stream.
• Delineated by discontinuities in either flow or substratum.
![Page 10: Water Resources Lecture 4](https://reader035.fdocuments.us/reader035/viewer/2022081503/56815d7e550346895dcb8ac7/html5/thumbnails/10.jpg)
Hydraulic BiotopesSubstrate Types• Bedrock• Boulder• Large Cobble• Pebble• Gravel• Sand • Silt/Mud
Flow Types• No flow• Barely perceptible flow• Smooth boundary turbulent• Ripple surface• Slow and fast riffle flow• Undular standing wave• Broken standing wave• Cascade• Chute• Free fall• Boil
![Page 11: Water Resources Lecture 4](https://reader035.fdocuments.us/reader035/viewer/2022081503/56815d7e550346895dcb8ac7/html5/thumbnails/11.jpg)
![Page 12: Water Resources Lecture 4](https://reader035.fdocuments.us/reader035/viewer/2022081503/56815d7e550346895dcb8ac7/html5/thumbnails/12.jpg)
![Page 13: Water Resources Lecture 4](https://reader035.fdocuments.us/reader035/viewer/2022081503/56815d7e550346895dcb8ac7/html5/thumbnails/13.jpg)
![Page 14: Water Resources Lecture 4](https://reader035.fdocuments.us/reader035/viewer/2022081503/56815d7e550346895dcb8ac7/html5/thumbnails/14.jpg)
![Page 15: Water Resources Lecture 4](https://reader035.fdocuments.us/reader035/viewer/2022081503/56815d7e550346895dcb8ac7/html5/thumbnails/15.jpg)
The Rive Continuum Concept (Vannote et al, 1980)
• 4 dimensions to change in a river system.• RCC Deals with longitudinal change: Basic Principle:
Rivers possess a continuous gradient of physical and chemical conditions that are progressively and continuously modified modified downstream.
Driving variablesResponse variables
![Page 16: Water Resources Lecture 4](https://reader035.fdocuments.us/reader035/viewer/2022081503/56815d7e550346895dcb8ac7/html5/thumbnails/16.jpg)
From: Davies and Day, 1998.
![Page 17: Water Resources Lecture 4](https://reader035.fdocuments.us/reader035/viewer/2022081503/56815d7e550346895dcb8ac7/html5/thumbnails/17.jpg)
RCC
• Essentially all components of a river, at any point along its length, are dictated by abiotic and chemical conditions and modified by gradients of biological variables and processes that occur upstream of the point of consideration.
![Page 18: Water Resources Lecture 4](https://reader035.fdocuments.us/reader035/viewer/2022081503/56815d7e550346895dcb8ac7/html5/thumbnails/18.jpg)
Criticism of RCC:
It does not focus on all 4 dimensions of change.
E.g: Junk et al, 1989: Flood Pulse Concept.
![Page 19: Water Resources Lecture 4](https://reader035.fdocuments.us/reader035/viewer/2022081503/56815d7e550346895dcb8ac7/html5/thumbnails/19.jpg)
From Davies and Day 1998
![Page 20: Water Resources Lecture 4](https://reader035.fdocuments.us/reader035/viewer/2022081503/56815d7e550346895dcb8ac7/html5/thumbnails/20.jpg)
Readings:
• Davies and Day, 1988• Frissel et al, 1986• Rowntree and Wadeson 1999• Vannote et al, 1980• Junk et al, 1989