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Lectures 34 & 35 - Freshwater Systems & Water Resources.docx

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Monika Havelka

ENV100 Chapter 12 Notes Jan 10 & 13, 2014 Lectures #34 & 35 - Freshwater Systems & Water Resources Water is what makes us unique − We are not the only planet that has water but the only planet that has water in abundance. − Shapes the surface of the Earth − Allows for life − Makes Earth different from all other planets! (water in abundance). − Exists in all 3 states (vapour, liquid, solid) − Atmosphere − On surface − Under the ground Water in atmosphere − Important in moving heat from equator to the poles − Regulates temperature − Rises as vapour; falls as rain/snow Water on surface • Ocean currents • Sculpts terrestrial landscape → soil formation, erosion • Carrier for many substances Water is locked up in minerals in the Earth’s mantle • Makes the mantle elastic; affects the dynamics of plate tectonics • Contributes to the mantle elasticity. Mantle is very hot → water is in a vaporous form. • Water is ubiquitous & water has a dynamic component which affects the movement of organisms & processes on the Earth. Hydrology is “water science” • Study of water in the hydrosphere, both on and under the ground • Movement, distribution, quantity, quality → study the impact on humans. • Reservoirs, processes, ecosystems Water is abundant on Earth, but drinkable water is rare • Managing freshwater systems involves maintaining: − Quantity & quality of water for drinking and other uses →supports a healthy pop. − Integrity of freshwater ecosystems • Freshwater = few dissolved salts Page 1of 10 ENV100 Chapter 12 Notes Jan 10 & 13, 2014 − Only 2.5% of Earth’s water is fresh − Most of this is tied up in glaciers and ice caps − There is a possibility of desalinizing ocean water → energy intensive → not a great way of effectively getting large amounts of drinking water. − That flux in and out of glaciers has significant impacts on the climate, the distribution of biota & sea- levels. Water is unevenly distributed in the hydrosphere. 97.5% - Oceans 2.5% - Fresh Water → 80% in Glaciers The hydrologic cycle We can approach the hydrologic cycle from a systems perspective • Reservoirs: - Ocean(biggest reservoir); ice caps and glaciers; and then groundwater • Processes: all those things that move water around the hydrologic cycle - Precipitation, surface runoff, infiltration, percolation, evaporation, transpiration • Fluxes: - The global hydrologic cycle maintains mass balance– total amount of water is fixed Page 2 of10 ENV100 Chapter 12 Notes Jan 10 & 13, 2014 - Local variations affect supply, and cause problems like floods and droughts Solar energy and gravity drive the hydrologic cycle • Solar energy drives evaporation, transpiration, condensation (allows movement of water from surface to the atmosphere). • Gravity drives precipitation, runoff, groundwater percolation (movement of water from the atmosphere to the surface). Surface freshwater • Rivers and streams • Springs • Lakes and ponds / Wetlands Rivers shape the landscape • Rivers are major agents of change of a landscape. Rivers are affected by topography but also create topography/landscape as well. • Water from rain, snowmelt, and springs runs off over the surface • Surface runoff (sheetflow) organizes into rills and gullies, then streams and rivers − Tributary = a smaller river flowing into a larger one • Erosion is the work of rivers carrying sediment to the ocean. Creates huge fluxes in topsoil etc. Adrainage basin is a local hydrologic unit • Drainage basin or catchment or watershed = area drained by one river • Drainage basic/catchment - where all the water in an area tends to gather. • Catchments are separated from one another by divides Catchments have inputs & outputs Have an urban area → develop parking-lots, cut down trees → transpiration rate goes down b/c there is no transpiring vegetation. Flat asphalt surface (used to be soil before) → infiltration rate will go down. If the precipitation doesn't infiltrate into the soil → surface run-off → greater rate of flow into the catchment. Precipitation = Inputs Evaporation + Transpiration & Runoff = Outputs (leaving the catchment). If there is an unbalanced relationship: − Excess of precipitation → storage will go up. If storage is filled, then it will have to go through evap + transpiration. − Lack of precipitation → less run-off/ less evapo-transpiration/ storage will go down. Groundwater • Groundwater = water located beneath the Earth's surface in soil pore spaces and in the fractures of rock formations. • Largest unfrozen freshwater reservoir (easily accessible source of drinking water) Page 3 of10 ENV100 Chapter 12 Notes Jan 10 & 13, 2014 • Aquifer = underground reservoir of rock and sediment • Residence time may be thousands of years • Canada: much more water underground than on the surface • 26% of Canada’s population depends on groundwater (mostly rural). Majority of urban people live near the great lakes therefore they depend on the great lakes for water. ConfinedAquifer - under pressure → geyser, artisanal well. Unconfined Aquifer - just soil overlying them, not under the same kind of pressure → easier to infiltrate & recharge. − Canada - we're really rich in ground-water as well/we have a lot of water in our aquifers. − Rural people's livelihood + jobs + economy depends on groundwater. Rural people are paying the price when we contaminate our groundwater. Aquifers are porous and permeable, water-saturated rock or sediment units • Aquifers store and transmit water. If aquifers are put under pressure, then they can explode & water might leak. -Porosity = % pore space -Permeability = interconnectedness of pores.Ameasure of how easily the water moves around in there • Aerated zone = some air, some water • Saturated zone = completely filled with water -Water table: top of the saturated zone. Where the saturated zone meets the aerated zone. Note: Sponge ex. Capillary Fringe - a zone where water is getting drawn up from the water table into the unsaturated zone through capillary action. Groundwater flow is Water table - physical plate where the zone ofntrolled by gravity aeration and the zone of saturation meet. • Water table mimics topography When the aquifer's really charged → water table rises. When the aquifer's depleted → -Where water table intersects surface = surface water • water table falls. Recharge = water flows into an aquifer via precipitation/infiltration • Discharge = water flows out of an aquifer via percolation/streams/springs/ocean Image: Canada - water is mostly used for industry. Alot of water is uPagein4oof10xtraction. India - largely agricultural use (irrigation). Lithuania - domestic purposes. ENV100 Chapter 12 Notes Jan 10 & 13, 2014 Water is unequally distributed : Many areas w/ high population density are water-poor & face serious water shortages. Ex: SaudiArabia. UN sees water as a fundamental human right. Water use exceeds supply in many areas: Canada. • 1.2 billion people, (20% world pop’n), live in areas of physical scarcity (500 million people are approaching this situation) • 1.6 billion people, (~25%) face economic water shortage (lack necessary infrastructure to take water from rivers and aquifers). • ~ 800 million people do not have access to safe drinking water  > 3.5 million people die each year from preventable water-related disease Global water management challenges include: • Urban and rural drinking water and sanitation • Water for industry and agriculture • Protection of aquatic ecosystems • “Holistic” watershed management • Impacts of environmental change on water resources Canada is criticized for wasteful water consumption • Per capita water use is 28% higher than the average OECD country • Since 1980, Canada’s water use has increased 5x faster than OECD ave. rate of increase Lecture #35 - Freshwater Systems & Water Resources Human use of surface water has environmental impacts • Downstream and trans-boundary impacts − Rivers are directional (upstream/downstream) - if you're putting pollutants/damming a river then the effects will be felt downstream. Watershed → water collection basin → effects will be felt inside the watershed. − Trans-boundary impacts → policies → what people do on 1 side of a national/provincial border, the effect will occur in 1 place but the people on the other side of the border will have to deal w/ the impacts. Canada & the U.S → rivers cross over b/c of directional nature of river flow → impacts policies. • Decreased flow Page 5 of 10 ENV100 Chapter 12 Notes Jan 10 & 13, 2014 − Taking water out for industrial applications/hydroelectric power affects the flow. Whenever we divert a river, we decrease the flow of a river. Impacts on ecology, soil penetration/soil infiltration etc. • Changes in erosion and siltation rates − If we're altering the landscape or the speed of the river → altering how fast erosion takes place. − When you channel a stream (straight path instead of a curvy one) → as the river picks up speed, erosion will occur at a faster rate. • Changes in water s
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