Midterm Flashcards
Q (groundwater flow) =
-K * A^(Δh / Δl) (Darcy’s Law)
tau (residence time) =
V / Q (volume / discharge)
Recurrence interval
Interval on which a flood of a given discharge occurs at least once; inversely related to exceedance probability
probability of a given flood occurring over a period of n years
1 - (1 - exceedance probability) ^ n
log plot equation
x = 10^(p * (log after - log before) + log before)
h (hydraulic head) =
z (elevation head; datum to bottom of piezo-/mano- meter) + Ψ (pressure head)
Potential evapotranspiration (PET)
Evapotranspiration that would occur from a wet surface under specific conditions
Water bonding
Polar covalent within molecules; hydrogen bonding between molecules
effects of H-bonding on water
high Bp, high freezing point, high viscosity, expansion upon freezing (crystalline structure maximizes H-bonding), surface tension, solvent ability
Water cycle pools
Lakes, rivers, groundwater, snowpack, ocean, atmosphere
Water cycle fluxes
Precipitation, evapotranspiration, streamflow, recharge
Water use goals
Not too much, not too little, of the right quality
Virtual water
Hidden flow of water in commodities
in-situ use
water use without withdrawal (i.e., waterwheel)
consumptive use
water use that diminishes quality or amount
nonconsumptive use
water use that does not diminish quality or amount
River functions
Geomorphological agent, human resource (often controlled), habitat, mover of water and substances quickly through landscape
Thalweg
Lowest point of river bottom; where length is measured
River variation by:
sinuosity, slope, width, depth, cross section
Climatic variability of rivers
Arid climates: very variable streamflow (little storage)
Cold climates: peak in summer or spring from melting
Temperate humid: generally consistent; can decrease in summer due to increased ET
Equatorial: most consistent; further out from equator has monsoons
Uncontained aquifer
In contact with atmosphere; water table is at equilibrium with atmospheric pressure
Contained aquifer
Under pressure due to confining units; have a potentiometric surface rather than a water table; often recharged by a distant area
Artesian well
Well in a confined aquifer where potentiometric surface is above ground level
Water table
top of saturated zone in equilibrium with atm
Capillary fringe:
Saturated area above water table resulting from capillary action
Flood analysis procedure
- Annual peak flow
- Rank
- Recurrence interval
- Exceedance probability
Flood types
Fluvial (river), pluvial (runoff / surface), coastal
Reasons for changing flood frequency
Climate shift, land cover change, dam construction
Conditions necessary for precipitation
Precipitable water, continuing moisture supply (atmospheric rivers, ocean water, “recycled” water from land surface), condensation (convergence - ICTZ, fronts - convection (monsoons), orographic (elevation, rain shadows beyond mountains), hydrometeor growth processes
Precipitation measurement
Bucket, rain gauge (tipping bucket), disdrometer, radar, satellites
Evapotranspiration measurement
Evapotranspiration pan, lysimeter, porometry and sap flux
Snow measurement
Snow tubes, snow pillows, satellite radiometers, LIDAR flights
Snow water equivalent
Depth of water that would have the same mass as the column of snow
Measurement tradeoffs
Rates vs. totals, labor vs. expense, spatial coverage vs. resolution, measuring vs. modeling
Lakes
Low velocity surface water surrounded by land
Lake sources and sinks
Groundwater, ET, runoff, inflow stream, and outflow stream
Lake productivity
Oligotrophic, mesotrophic, eutrophic
Lake characteristics
Water sources and sinks, lake productivity, mixing, landscape position, residence time, drainage basin / lake area, salinity
Lake formation methods
Glaciers, volcanic and tectonic processes, landslides and mudslides, oxbow, closed basin (endorheic)
Reservoir/dam purposes
Recreation, flood control, ecological purpose, irrigation, domestic supply, hydroelectric, navigation
Dam/reservoir components
Dam, outlet works, spillway, live storage, dead storage, flood pool
Upstream dam/reservoir problems
Migratory blocking, displaced people, trap sediment, change habitat, induce demand for water, expensive, more ET, eutrophication, loss of land, pollutant concentration
Downstream dam/reservoir problems
Less sediment (starve deltas), altered flow, changes in downstream temp + dissolved gas, dam failure & hazard, dam-induced seismicity
Ecosystem
Community of interdependent species, together with the non-living environment, having a relatively self-contained energy flow and being distinct from neighboring communities
River reach
Stretch of a river or stream with the same properties
Wetland services
Absorb nutrients and pollutants (natural filtration), dissipate wave energy, serve as flood storage, and provide habitat
Wetland characteristics
Tidal (mangrove, salt marsh) or not, wet seasonally or year round, saturated (marshes and wet meadows) or inundated (bogs and fens), fed by precipitation (bog) or overland flow (marsh) or groundwater (fens), woody (swamp) or soft-stemmed (marsh), organic (peat) (bogs, fens) or mineral soils (swamps, marshes)
Ramsar convention
Protects wetlands; signed by 172 countries; response to loss of 50% of wetlands since 1900
Hyporheic flow
Exchange between river flow and shallow subsurface: important transfer of gas, solutes, contaminants, microorganisms, and particles
Riffle
Shallow and quick flowing part of a river
Discharge/streamflow measurement
Weirs and buckets; velocity-area relationships with blocks: Q = depth * width * velocity; rating curves
