Chapter 3:Hydrology

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Chapter 3Hydrology
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Outline

• Water use and availability
• The hydrologic cycle
• Rainfall
• Surface water
• Draught
• Reservoirs
• Groundwater
• Relevant websites

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Introduction

• Water Use and Availability
• WATER USE IN 1990 USGS fact sheet
• About 339,000 million gallons per day (Mgal/d)
• about one quarter of the national renewable
  supply
• about 220 billion gallons per day (70) was
  returned to streams after use.
• 1990 withdrawal were about 7 percent lt during
  1980,
• Four major water-use categories
• Domestic and commercial,
• irrigation and livestock,
• industrial and mining, and
• thermoelectric power.

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http//water.usgs.gov/pubs/circ/circ1223/html/p06-
8a.htmltable1 Surface-water indicators Streamflow
Reservoir storage, construction, sedimentation,
and removal Storage in large lakes, perennial
snowfields, and glaciers Ground-water
indicators Ground-water-level indices Changes in
ground-water storage Number and capacity of
supply wells and artificial recharge
facilities Water-use indicators Total withdrawals
by source hydropower) Reclaimed
wastewater Conveyance losses Consumptive uses
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http//observe.arc.nasa.gov/nasa/earth/hydrocycle/
hydro3.html
Hydrologic Cycle
Precipitation
Interception
Constructed
Forested
ET
Pre-event Water
Return Flow
Upper Soil Storage
Saturated Area
FC
Lower Soil Storage
Subsurface Flow
Percolation
Total Event Runoff
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Rainfall

• Depth inches, cms
• Volume depth Area
• Intensity Depth per unit time
• Recurrence Interval return period 10-year storm
• Probability of Occurrence 1/return period
• Intensity Duration Frequency Relationship
  Available from National Weather service. Patterns
  vary for climate and location X axis mm/hr Y axis
  Duration I A/(tB) I in mm/h, t min A and B
  constants
• Rainfall Maps and Classification Return period
  Vs duration severity index in log

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Surface Water

• Watersheds Drainage basin, Drainage divide, Use
  topomaps
• Streamflow Flow rate or discharge Lag time,
  Peak, mean flow, timing to peak
• Hydrographs
• Gauging Stations

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Three Attributes of Streamflow
1. Peak Flow
2. Mean Daily Flow Total Q/t
Streamflow (Q) M3/sec
3. Time to Peak
Time (t) days
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Hydrologic cycle as integrator of processes of
land-water interaction
Floods Water quality Sediment Habitat ...
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Draughts

• MA7CD10 Flow Minimum Average 7-consecutive day
  10 year flow
• Means 90 of times the flow will be greater than
  7 day minimum flow

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Reservoirs

• Reservoirs Conservation , multipurpose,
  Distribution storage, detention storage
• Dams have environmental impacts
• Summation Hydrographs
• S curve
• Reservoir capacity curve X vol Y surface
  elevation

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Case Study

• EIA of A Reservoir

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Groundwater

• Aquifers
• Groundwater flow
• Permeability
• Darcys Law V(flow vel.) K(perm) Slope

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Wells

• Static level before pumping begins
• Drawdown cone of depression
• Radius of influence
• Safe yield
• Specific yield withdrawal rate/Draw down

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Related Web Sites

• American water Resources Association
• Bureau of Reclamation
• EPA Surf your watershed
• USGS Hydrology Primer
• USGS Water Resources of the US
• National Weather Service office of hydrology
• National Ground water Association
• Hydrogeologists Home Page
• Hydrology Laboratory

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Other aspects

• Integrated perspective
• Linking past present and future
• Link the cause effect relationship
• Water has three attributes
• Quantity, quality and timing
• Hydrologic Change management
• Water Quality Management Plan as a way to control
  water quality