Introduction to Water Resources http://www.colostate.edu/Depts/SoilCrop/extension/Newsletters/2000/irrigation.JPG http://www.starlinetours.com/images/LasVegas/HooverDam-Front.jpg http://www.fs.fed.us/wildflowers/regions/pacificnorthwest/MetoliusRiver/images/metolius_river_pine_lg.jpg A Quick Review Physical Geography The science concerned with the spatial aspects and interactions of the physical elements and processes that make up the environment: energy, air, water, weather, climate, landforms, soils, animals, plants, microorganisms, and Earth Water Resources Introduction Water as a resource The term resource takes on many different definitions A source of supply or support A natural source of wealth A natural feature or phenomena that enhances the quality of life Water A liquid that descends from the clouds to form rivers, lakes, seas and is a major constituent of living organisms, etc. http://rst.gsfc.nasa.gov/Sect3/aster_mexicali.jpg Explain the Image: ___________________________________________________ ____________________________________________________________________ ____________________________________________________________________ The Hydrologic Cycle A hydrologic cycle model 97% of Earth’s water is in the oceans 86% of all evaporation occurs over the ocean 14% over land and includes the process of transpiration 100% The Hydrologic Cycle The Hydrologic Cycle Surface water Precipitation that reaches Earth’s surface follows two basic pathways: 1. Overland flow Surface water runoff that is flowing over the landscape 2. Soaks into the ground Influence plant growth and survival Influence well depth The Hydrologic Cycle Surface water Overland flow Occurs when the precipitation rate exceeds the infiltration rate Vegetated surfaces allow more water to infiltrate than bare surfaces Coarse-textured soil (i.e., sand) allow water to infiltrate more quickly than fine-textured (i.e., clay) soils Construction sites and urban areas produce a lot of overland flow Construction sites and bare ground Urban areas are generally impervious The Hydrologic Cycle Rainsplash Erosion - Splash erosion results from the bombardment of soil surfaces by rain drops - Heavier drops travel at higher speeds than small drops - Large drops carry hundreds of times more energy than small drops - Erosion is greatest during short-duration, high intensity thunderstorms. - Raindrop impacts break up clumps of soil The lighter materials — such as fine sand, silt, clay and organic material — that are detached by raindrop are more readily carried away by runoff, leaving behind larger sand grains, pebbles and gravel The Hydrologic Cycle http://plantandsoil.unl.edu/croptechnology2005/UserFiles/Image/siteImages/UrbanRillErosion-NRCS-LG.jpg Where does this sediment ultimately go (flow) once it hits the concrete? The Hydrologic Cycle Surface water Overland flow Erosion associated with overland flow Sheet erosion Removal of a uniform layer of soil from the land surface as a result of rainsplash or runoff Rill erosion Gully erosion The Hydrologic Cycle Surface water Overland flow Erosion associated with overland flow Sheet erosion Rill erosion The development of small grooves spaced fairly uniformly along the slope It is caused when runoff is heavy and water concentrates in rivulets The Hydrologic Cycle Surface water Overland flow Erosion associated with overland flow Sheet erosion Rill erosion Gully erosion Gullies form when water in rills concentrate into larger channels The Hydrologic Cycle Surface water Water is intercepted as it falls from the sky by vegetation or some other ground cover Stem flow is intercepted water that drains across plant leaves and down their stems to the ground Throughfall is precipitation that falls directly to the ground The Hydrologic Cycle Surface water Water is intercepted as it falls from the sky by vegetation or some other ground cover Infiltration occurs when water soaks into the subsurface Percolation occurs when water that permeates soil or rock continues through a downward movement The Hydrologic Cycle Surface water Water infiltration The rate of water infiltration into the soil is a function of porosity and permeability Porosity is the amount of pore space in the soil or rock Permeability is the ability of soil or rock to receive, hold, or pass fluid Soil Textural Triangle Used to help describe soil texture The Hydrologic Cycle Surface water Water infiltration Permeability vs. porosity Permeability depends on particle-sizes and the shape and packing of grains in the soil or rock Coarse-textured soils (i.e., sand) have high permeability Fine-textured soils (i.e., clay) have low permeability The Hydrologic Cycle Surface water Water infiltration Permeability vs. porosity Porosity of soil In poorly sorted sediments, those with a larger range of grain sizes, the finer grains tend to fill the spaces between the larger grains, resulting in lower porosity The Hydrologic Cycle Faster infiltration Slower infiltration Groundwater Resources Groundwater Important part of the hydrologic cycle Lies beneath the surface, beyond the soil-moisture root zone Much more water exists below the ground than all the surface lakes and stream combined A volume of water comparable to 70 times all the freshwater lakes in the world http://theparagraph.com/wp-content/articles/post109/KE-Aerial-center-pivot.jpg http://www.ag.ndsu.edu/pubs/ageng/irrigate/ae91-1.jpg Groundwater Resources Groundwater Current groundwater issues Pollution threatens groundwater quality Point source pollution Non-point source pollution Overconsumption depletes groundwater volume in quantities beyond natural replenishment rates Overpumping Saltwater encroachment http://co.water.usgs.gov/nawqa/hpgw/photos/centerpivot.jpg Groundwater Resources Groundwater profile and movement Groundwater percolates downward as gravitational water Zone of aeration Zone above the water table that has air in its pore spaces and may or may not have water This zone is not saturated http://www.epa.gov/safewater/dwa/electronic/presentations/sdwa/pt1/img015.gif Unsaturated zone = zone of aeration Groundwater Resources Groundwater profile and movement Eventually the water reaches an area where subsurface water accumulates Zone of saturation A groundwater zone below the water table in which all pore spaces are filled with water This zone is completely saturated http://www.epa.gov/safewater/dwa/electronic/presentations/sdwa/pt1/img015.gif No air space left, filled by water Groundwater Resources Groundwater profile and movement Aquifer, aquiclude, and water table Aquifer A rock layer (or sediment type) that is permeable to groundwater flow Aquiclude A body of rock that does not conduct water in useable amounts Water table The upper limit of the water that collects in the zone of saturation Groundwater Resources Sandstone vs. Shale What rock makes the better aquifer and why? ______________________________________________ Groundwater Resources Confined and unconfined aquifers Confined aquifer Bound above and below by impermeable layers of rock or sediment Example of impermeable layer is: _____________ Unconfined aquifer Permeable layer on top and an impermeable layer beneath Example of permeable layer is: _____________ Groundwater Resources Are both confined and unconfined aquifers represented above? ______________________________________________ Groundwater Resources Confined and unconfined aquifers Recharge Ground surface where water enters an aquifer http://faculty.rmc.edu/mfenster/hydrologic/hydrologiccycle.jpg http://groundwater.orst.edu/under/images/rechargeb.gif Confined aquifers have recharge areas that are more restricted than recharge areas associated with unconfined aquifers. True or False Groundwater Resources Confined and unconfined aquifers Wells in aquifers Unconfined aquifers Require pumps to make the water rise above the water table Confined aquifers Water is under pressure from being confined and the water can rise on its own Potentiometric surface http://www.bartleby.com/images/A4images/A4artwel.jpg Groundwater Resources Springs Where the water table intersects the land surface This intersection includes streams and lakes Ultimately groundwater may enter stream channels to flow as surface water During dry periods (i.e., little rainfall) groundwater may sustain the flow of streams http://www.bartleby.com/images/A4images/A4artwel.jpg http://www.tpwd.state.tx.us/learning/webcasts/rivers02/bigsprings.phtml Explain the Picture Groundwater Resources Overuse of Groundwater Overpumping leads to drawdown Drawdown occurs if the pumping rate exceeds the replenishment flow of water into the aquifer or the horizontal flow around the well Result is a cone of depression http://www.groundwateruk.org/images/illustrations/gwf012.jpg Groundwater Resources Overuse of Groundwater Collapsing aquifers If water is pumped out of the rock or sediment, its support can be lost Remember that water in the pore space of rock or sediment adds structural support Land subsidence Cracked foundations of homes http://images.google.com/imgres?imgurl=http://ga.water.usgs.gov/edu/pictures/landsubsidence.jpg&imgrefurl=http://ga.water.usgs. gov/edu/earthgwlandsubside.html&h=348&w=160&sz=11&hl=en&start=39&tbnid=UgZE49odhXJIiM:&tbnh=120&tbnw=55&prev=/ images%3Fq%3Dgroundwater%2Bsubsidence%26start%3D20%26gbv%3D2%26ndsp%3D20%26hl%3Den%26sa%3DN Groundwater Resources Overuse of Groundwater Saltwater encroachment Occurs when aquifers are over-pumped near oceans or seas Along the coastline, freshwater and saltwater establish a “zone of dispersion” that separates the two Saltwater is more dense than freshwater Note “upcone” http://hays.outcrop.org/images/keller3e/12_13ab.jpg Aquifer becomes useless as a freshwater source!