The Colorado Front Range Runoff Case Study.ppt
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This document discusses surface water and streamflow generation. It summarizes that a watershed is the area of land that drains into a stream, and streamflow is the movement of water through channels via surface and subsurface flow, influenced by climate, land cover, and soil. Streamflow is generated through three main mechanisms: 1) Hortonian overland flow during heavy rain on impervious surfaces, 2) subsurface flow through lateral movement of water in the soil, and 3) saturation overland flow when the soil is saturated from below and precipitation becomes overland runoff.
The Colorado Front Range Runoff Case Study.ppt
- 1. Surface water Watershed – area of land draining into a stream at a given location Streamflow – gravity movement of water in channels Surface and subsurface flow Affected by climate, land cover, soil type, etc.
- 3. Streamflow generation Streamflow is generated by three mechanisms 1. Hortonian overland flow 2. Subsurface flow 3. Saturation overland flow Some texts mention groundwater ridging as an additional mechanism contributing to streamflow
- 4. Welcome to the Critical Zone
- 5. Denudation Weathering front advance Erosion and weathering control the extent of critical zone development
- 6. Sediment Water, solutes and nutrients Critical zone architecture influences sediment sources, hydrology, water chemistry and ecology
- 7. Boulder Golden The Colorado Front Range Fort Collins
- 8. Boulder Golden Fort Collins The Boulder Creek watershed Limits of glacial and fluvial rejuvenation •Precambrian crystalline bedrock •Uniform climate history •Three erosional states
- 9. Boulder Creek Critical Zone Observatory Slope map draped over shaded relief. Glacial limits •How do weathering and transport processes control the structure of the CZ? •What is the impact of CZ structure on hydrological, geochemical and biological functions?
- 11. Three experiments in one: the geomorphic context of Boulder Creek Upper: glaciated Middle: steady, old Lower: rejuvenated
- 12. Front Range ‘Rocky mountain surface’
- 14. fracture zone 5m 5m bedding weathered rock soil water flow path Oregon Coast Range- Coos Bay Anderson et al., 1997, WRR. Montgomery et al., 1997, WRR Torres et al., 1998, WRR Channel head
- 15. Hortonian Flow Sheet flow described by Horton in 1930s When i<f, all i is absorbed When i > f, (i-f) results in rainfall excess Applicable in impervious surfaces (urban areas) Steep slopes with thin soil hydrophobic or compacted soil with low infiltration Rainfall, i Infiltration, f i > q Later studies showed that Hortonian flow rarely occurs on vegetated surfaces in humid regions.
- 16. Subsurface flow Lateral movement of water occurring through the soil above the water table primary mechanism for stream flow generation when f>i Matrix/translatory flow Lateral flow of old water displaced by precipitation inputs Near surface lateral conductivity is greater than overall vertical conductivity Porosity and permeability higher near the ground Macropore flow Movement of water through large conduits in the soil
- 17. Soil macropores
- 18. Saturation overland flow Soil is saturated from below by subsurface flow Any precipitation occurring over a saturated surface becomes overland flow Occurs mainly at the bottom of hill slopes and near stream banks
- 19. Streamflow hydrograph Graph of stream discharge as a function of time at a given location on the stream Perennial river Ephemeral river Snow-fed River Direct runoff Baseflow