EART 204 Water Dr. Slawek Tulaczyk Earth Sciences, UCSC 1
Water is an amazing liquid, (high heat capacity - particularly in phase transitions, maximum density at ca. 4 deg. C) 2
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Basin Hydrologic Cycle Charbeneau, 2000. 10
Basin Hydrologic Cycle GW/SW Interaction 11
Global Hydrologic Cycle Schematic Domenico and Schwartz, 1990. 12
Basin Hydrologic Cycle Schematic Domenico and Schwartz, 1990. 13
Basin Hydrologic Cycle Quantitative Representation Basin Surface/ Soil I Aquifer Domenico and Schwartz, 1990. 14
2. Soil Horizons 15
Charbeneau, 2000. 16
Figure 15.1 17
3. Aquifers 18
Aquifers Definition: A geological unit which can store and supply significant quantities of water. Principal aquifers by rock type: Unconsolidated Sandstone Sandstone and Carbonate Semiconsolidated Carbonate-rock Volcanic Other rocks 19
Occurrence of Ground Water Ground water occurs when water recharges the subsurface through cracks and pores in soil and rock Shallow water level is called the water table 20
Recharge Natural Precipitation Melting snow Infiltration by streams and lakes Artificial Recharge wells Water spread over land in pits, furrows, ditches Small dams in stream channels to detain and deflect water 21
Example Layered Aquifer System Bedient et al., 1999. 22
Other Aquifer Features 23
Leaky and Perched Aquifers Leaky confined aquifer: represents a stratum that allows water to flow from above through a leaky confining zone into the underlying aquifer Perched aquifer: occurs when an unconfined water zone sits on top of a clay lens, separated from the main aquifer below 24
4. Soil Texture 25
Bedient et al., 1999. 26
Particle Size Distribution Poorly sorted silty fine to medium sand Well sorted fine sand Bedient et al., 1999. 27
Particle Size Distribution Charbeneau, 2000. 28
4. Porosity and Density 29
REV Representative Elementary Volume Charbeneau, 2000. 30
REV Scale Effect Freeze and Cherry, 1979. 31
Types of Porous Media Freeze and Cherry, 1979. 32
Typical Values of Porosity Bedient et al., 1999., 33
6. Saturation and Water Content 34
Soil Moisture Held by Capillary Pressure Charbeneau, 2000. 35
Moisture Content in Capillary Zone Charbeneau, 2000. 36
7. Hydraulic Head 37
Pressure and Elevation Heads - Laboratory ψ = pressure head z = elevation head h = total head Freeze and Cherry, 1979. 38
Pressure and Elevation Heads - Field ψ = pressure head z = elevation head h = total head Freeze and Cherry, 1979. 39
Two Confined Aquifers with Different Heads Groundwater will tend to flow from the top aquifer to the bottom aquifer. We can t make any conclusion about horizontal head gradients from this picture. Charbeneau, 2000. 40
Horizontal and Vertical Head Gradients Freeze and Cherry, 1979. 41
Horizontal and Vertical Head Gradients Freeze and Cherry, 1979. 42
Lecture 2 Reading Assignments Hydrologic Cycle and Water Distribution Bedient et al., pp. 1-6 Domenico & Schwartz, pp. 9-21 Soil Horizons Bedient et al., pp. 15-18 Charbeneau, pp. 5-6 Aquifers/Soil Texture/Porosity and Density/Saturation and Water Content Bedient et al., pp. 18-23 Charbeneau, pp. 2-12 Hydraulic Head Bedient et al., pg. 24 Domenico and Schwartz, pp. 58-59 Freeze and Cherry, pp. 18-25 Note: Only reading in Bedient et al. is required. Other reading assignments are highly recommended and contain extended explanations that might be helpful for your understanding of the material. 43
Hydrology Hydrologic Cycle Precipitation Average over Area Return Period Abstractions from Rainfall Runoff Hydrographs Determination methods 44
Hydraulics of Structures Weir flow Orifice flow Pipe flow Spillway flow Stage-Discharge relationship 45
Open Channel Flow Channel geometries Triangular Trapezoid Parabolic Manning s equation Manning roughness, n Grass waterway design 46
Precipitation Input to the Rainfall-Runoff process Forms include: Rainfall Snow Hail Sleet Measured directly Varies temporally and areally 47
Rainfall Data Daily Hourly 15-minute Continuous Reported as depth, which is really volume over a given area, over a period of time 48
Average Rainfall Simple arithmetic average Theissen Polygon 49
Example 1 How do different calculation methods of rainfall average compare? Consider: 50
US 100yr-24hr Rainfall 100yr-24hr data from TP-40 (Hershfield (1961) as referenced by Fangmeier et al. (2006) 51
Runoff If rainfall rate exceeds the soil infiltration capacity, ponding begins, and any soil surface roughness creates storage on the surface. After at least some of those depressions are filled with water, runoff begins. Additional rain continues to fill depressional storage and runoff rate increases as more of the hill slope and subsequently the watershed contributes runoff. 52
Rainfall/Runoff process 53
Open Channel Flow Flow through open channels is another important area to consider and review. Velocity and flow rate are usually calculated using Manning s equation, which considers flow geometry, channel roughness and slope. 54
Manning s Equation Where: V= flow velocity in fps R h = Hydraulic Radius in ft S = Energy gradeline slope in ft/ft (=bed slope for normal flow) n = Manning coefficient 1.49 = conversion from SI to English units Hydraulic radius is the flow area divided by the wetted perimeter. 55
Open Channel Flow Channel Geometry 56
Manning n values 57
Example What is the flow rate for a rectangular finished (clean) concrete channel with a base width of 8, channel slope of 0.5%, with a normal water depth of 2? A: 140 cfs B: 8.5 cfs C: 100 cfs D: 200 cfs 58
Solution n is 0.015, Rh is 8*2 sq.ft./(2+8+2) ft, S is 0.005 ft/ft, so V = 8.5 ft/sec Q = V*A= 8.5 ft/sec*16 sq.ft. = 140 cfs 59