Ground Water

Water Resources Water –Earth’s surface is covered by 71% water –Essential for life – can survive only a few days without water

Supply of Water Resources Small fraction (.014%) is readily available for human use

Evaporation and transpiration Evaporation Stream Infiltration Water table Infiltration Unconfined aquifer Confined aquifer Lake Well requiring a pump Flowing artesian well Runoff Precipitation Confined Recharge Area Aquifer Less permeable material such as clay Confirming permeable rock layer Water Cycle – continuously collected, purified, recycled and distributed

Watershed A watershed describes the total area contributing drainage to a stream or river May be applied to many scales –A large watershed is made up of many small watersheds

Evaporation and transpiration Evaporation Stream Infiltration Water table Infiltration Unconfined aquifer Confined aquifer Lake Well requiring a pump Flowing artesian well Runoff Precipitation Confined Recharge Area Aquifer Less permeable material such as clay Confirming permeable rock layer Zone of saturation (spaces completely filled with water)

Water sources Groundwater water held underground in the soil or in pores and crevices in rock. Water table – top of zone of saturation Aquifer – water saturated layers of sand, gravel or bedrock through which groundwater flows. video

Use of Water Resources Humans directly or indirectly use about 54% of reliable runoff Withdraw 34% of reliable runoff for: Agriculture – 70% Industry – 20% Domestic – 10% Leave 20% of runoff in streams for human use: transport goods, dilute pollution, sustain fisheries

Aquifer - body of saturated rock or sediment through which water can move easily –Permeability - the capacity of a rock to transmit fluid through pores and fractures –Porous - (of rocks) having small spaces or holes through which liquid or air may pass. –Rocks that do not let water pass through are impermeable.

permeable impermeable

Spring - a place where water flows naturally from rock or sediment onto the ground surface

Too Little Water Problems in the West Dry climate Drought Desiccation Acute shortage Adequate supply Shortage Metropolitan regions with population greater than 1 million US has plenty of water. Much of it is in the wrong place at the wrong time. Most serious problems are flooding, pollution, occassional urban shortages

Water conflicts: Global Two main factors for water shortage: dry climate and too many people. Many people live in hydro poverty – can’t afford clean water.

Too Much Water: Floods Natural phenomena Aggravated by human activities Rain on snowLiving on floodplains Impervious surfaces Removal of vegetation Draining wetlands Floodplain Levee Flood wall Dam Reservoir

Stewardship Stewardship of the environment refers to protecting the environment through recycling, conservation, regeneration, and restoration. It means taking responsibility for our choices. The responsibility for environmental quality should be shared by all those whose actions affect the environment.

Deforestation and flooding

Using Dams and Reservoirs to Supply More Water: The Trade-offs Large losses of water through evaporation Large losses of water through evaporation Flooded land destroys forests or cropland and displaces people Flooded land destroys forests or cropland and displaces people Downstream flooding is reduced Downstream cropland and estuaries are deprived of nutrient-rich silt Downstream cropland and estuaries are deprived of nutrient-rich silt Reservoir is useful for recreation and fishing Can produce cheap electricity (hydropower) Migration and spawning of some fish are disrupted Provides water for year-round irrigation of cropland

Tapping Groundwater Year-round use No evaporation losses Often less expensive Potential Problems: Water table lowering – too much use Depletion – U.S. groundwater being withdrawn at 4X its replacement rate Saltwater intrusion – near coastal areas Chemical contamination Reduced stream flows

Solutions Sustainable Water Use Not depleting aquifers Preserving ecological health of aquatic systems Preserving water quality Integrated watershed management Agreements among regions and countries sharing surface water resources Outside party mediation of water disputes between nations Marketing of water rights Raising water prices Wasting less water Decreasing government subsides for supplying water Increasing government subsides for reducing water waste Slowing population growth

Pollution Source terminology Point source = pollution comes from single, fixed, often large identifiable sources –smoke stacks –discharge drains –tanker spills Non-point source = pollution comes from dispersed sources –agricultural runoff –street runoff

Types of Water Pollution Sediment –logging, roadbuilding, erosion Waste Water –human waste, storm sewers, runoff from agriculture, grazing and logging, many others Nutrient enrichment = Eutrophication –Nitrates or fertilizers are used by farmers to increase the nutrients in the soil. –leads to increased growth in aquatic systems, ultimately more non-living organic matter

Eutrophication Eutrophication - excessive buildup of nutrients in a lake or other body of water caused by nitrates (fertilizers), frequently due to runoff from the land, which causes a dense growth of plant life and death of animal life from lack of oxygen.

BOD As micro-organisms decompose (through respiration) organic matter, they use up all the available oxygen. Biological Oxygen Demand (BOD) Amount of oxygen required to decay a certain amount of organic matter. If too much organic matter is added, the available oxygen supplies will be used up.

Types of Water Pollution Disease-causing organisms –from untreated sewage, runoff from feed lots Toxic chemicals –pesticides, fertilizers, industrial chemicals Heavy metals –lead, mercury Elevated temperatures = Thermal Pollution –water is used for cooling purposes, then heated water is returned to its original source –any increase in temperature, even a few degrees, may significantly alter some aquatic ecosystems.

Groundwater Pollution Examples of wastewater –Agricultural products –Underground storage tanks –Landfills leaks –Septic tanks

Oil Spills Exxon Valdez released 42 million liters of oil in Prince William Sound, contaminating 1500 km of Alaska coastline in 1989 Was the cleanup effective? Most marine oil pollution comes from non- point sources: –runoff from streets –improper disposal of used oil –discharge of oil-contaminated ballast water from tankers

Growth of population Supply & demand are in growing conflict – supply is finite – water management driven by values and needs Increases demand/use of water Increases land use and changes vegetation and permeability Increases demand for instream values – instream flows are for people

The construction of dams have slowed the once flowing Columbia River into a series of lakes.

Agriculture uses approximately 70% of the water withdrawn from our streams and rivers

Changing land use changes vegetation and need for water

Change in land use also changes permeability

Avoid headwater disturbance and leave vegetation

Allow floodplains to function as floodplains