1. This lecture will help you understand:  Water and the hydrologic cycle  Water’s distribution on Earth  Freshwater ecosystems  Use and alteration of freshwater systems  The marine environment

2. Freshwater systems  Water may seem abundant, but drinkable water is rare  Freshwater = relatively pure, with few dissolved salts  Only 2.5% of Earth’s water is fresh  Most freshwater is tied up in glaciers and ice caps

3. Water storage  Water Reservoir – a place in the atmosphere, ocean or underground where water is stored for a period of time

4. Rivers & streams wind through landscapes  Water from rain, snowmelt, or springs forms streams, creeks or brooks  These merge into rivers, and eventually reaches the ocean  Tributary = a smaller river flowing into a larger one  Watershed = the area of land drained by a river and its tributaries

5. Rivers & streams wind through landscapes  Hydrology – the study of the occurrence, distribution and movement of water on, in & above the Earth

6. A river may shift course  Floodplain = areas nearest to the river’s course that are flooded periodically  Frequent deposition of silt makes floodplain soils fertile  Riparian = riverside areas that are productive and species-rich  Water of rivers and streams hosts diverse ecological communities

7. Wetlands include marshes, swamps, and bogs  Wetlands = systems that combine elements of freshwater and dry land  Freshwater marshes = shallow water allows plants to grow above the water’s surface  Swamps = shallow water that occurs in forested areas  Can be created by beavers  Bogs = ponds covered in thick floating mats of vegetation  A stage in aquatic succession

8. Wetlands are valuable  Wetlands are extremely valuable for wildlife  They slow runoff  Reduce flooding  Recharge aquifers  Filter pollutants  People have drained wetlands, mostly for agriculture  Southern Canada and the U.S. have lost more than half of their wetlands

9. Lakes and ponds are ecologically diverse  Lakes and ponds are bodies of open, standing water  Littoral zone = region ringing the edge of a water body  Benthic zone = extends along the entire bottom of the water body  Home to many invertebrates  Limnetic zone = open portions of the lake or pond where the sunlight penetrates the shallow waters  Profundal zone = water that sunlight does not reach  Supports fewer animals because there is less oxygen

10. A typical lake

11. Lakes vary in their nutrients and oxygen  Oligotrophic lakes and ponds = have low nutrient and high oxygen conditions  Eutrophic lakes and ponds = have high nutrient and low oxygen conditions  Eventually, water bodies fill completely in through the process of succession  Inland seas = large lakes that hold so much water, their biota is adapted to open water

12. Lake Baikal

13. Groundwater plays a key role  Groundwater = any precipitation that does not evaporate, flow into waterways, or get taken up by organisms  Groundwater makes up one fifth of the Earth’s freshwater supply  Aquifers = Porous sponge-like formations of rock, sand, or gravel that hold groundwater  Zone of aeration = pore spaces are partially filled with water  Zone of saturation = spaces are completely filled with water  Water table = boundary between the two zones  Aquifer recharge zone = any area where water infiltrates Earth’s surface and reaches aquifers

15. A typical aquifer

16. There are two categories of aquifers  Confined or artesian = water-bearing, porous rocks are trapped between layers of less permeable substrate (i.e., clay)  Is under a lot of pressure  Unconfined aquifer = no upper layer to confine it  Readily recharged by surface water  Groundwater becomes surface water through springs or human-drilled wells  Groundwater may be ancient: the average age is 1,400 years

17. The Ogallala Aquifer  The world’s largest known aquifer  Underlies the Great Plains of the U.S.  Its water has allowed farmers to create the most bountiful grain- producing region in the world

18. Water is unequally distributed across Earth’s surface  Different regions possess vastly different amounts of groundwater, surface water, and precipitation  Many areas with high population density are water- poor and face serious water shortages

19. Water is distributed unevenly in time, too  Monsoon seasons bring concentrated storms  Half a region’s annual rain may fall in a few hours  People erect dams to store water

20. Climate change will cause water shortages  Climate change will cause  Altered precipitation patterns  Melting glaciers  Early season runoff  Intensified droughts  Flooding  Increasing probability that there will be still less water for more people

21. How we use water  We have achieved impressive engineering accomplishments to harness freshwater sources  60 % of the world’s largest 227 rivers have been strongly or moderately affected  Dams, canals and diversions  Consumption of water in most of the world is unsustainable  We are depleting many sources of surface water and groundwater  Water is becoming non-renewable resource

22. Water supplies houses, agriculture, and industry  Proportions of these three types of use vary dramatically among nations  Arid countries use water for agriculture  Developed countries use water for industry

23. Different types of water use  Consumptive use = water is removed from an aquifer or surface water body, and is not returned  Non-consumptive use = does not remove, or only temporarily removes, water from an aquifer or surface water  Electricity generation at hydroelectric dams

24. Areas where water use exceeds supply

25. US WATER USAGE

26. We are depleting groundwater  Groundwater is easily depleted  Aquifers recharge slowly  1/3 of world population relies on groundwater  As aquifers become depleted  Water tables drop  Salt water intrudes in coastal areas  Sinkholes = areas where ground gives way unexpectedly  Some cities (Venice, Mexico City) are slowly sinking  Wetlands dry up

27. Will we see a future of water wars?  Freshwater depletion leads to shortages, which can lead to conflict  261 major rivers cross national borders  Water is a key element in hostilities among Israel, Palestinians, and neighboring countries  Many nations have cooperated with neighbors to resolve disputes

28. Oceans cover most of the Earth’s surface  The oceans influence global climate, team with biodiversity, facilitate transportation and commerce and provide resources  They cover 71% of Earth’s surface and contain 97% of Earth’s surface water  Oceans influence the atmosphere, lithosphere and biosphere

29. The oceans contain more than water  Ocean water is 96.5% water  Plus ions of dissolved salts  Evaporation removes pure water & leaves a higher concentration of salt  Nutrients (nitrogen & phosphorus)  Dissolved gas  Nitrogen - diffusion  Carbon Dioxide - diffusion  Oxygen is added by plants, bacteria & atmospheric diffusion  Salinity – the amount of dissolved inorganic solids in water  Freshwater < 0.5 ppt  Brackish 0.5 – 17 ppt  Ocean 35 ppt (3.5 %)

30. Ocean water is vertically structured  Temperature declines with depth  Heavier (colder saltier) water sinks  Light (warmer and less salty) water remains near the surface  Temperatures are more stable than land temperatures  Water’s high heat capacity  It takes much more heat to warm water than air  Oceans regulate the earth’s climate  They absorb and release heat  Ocean’s surface circulation

31. The ocean has several layers  Surface zone  Warmed by sunlight and stirred by wind  Consistent water density  Pycnocline = below the surface zone  Density increases rapidly with depth  Deep Zone = below the pycnocline  Dense, sluggish water  Unaffected by winds, storms, sunlight, and temperature

32. Ocean water flows horizontally in currents  Currents = the ocean is composed of vast riverlike flows  Driven by density differences, heating and cooling, gravity, and wind  Influence global climate and El Niño and La Niña  Transport heat, nutrients, pollution, and the larvae of many marine species  Some currents such as the Gulf Stream are rapid and powerful  The warm water moderates Europe’s climate

33. The upper waters of the oceans flow in currents

34. Surface winds and heating create vertical currents  Upwelling = the vertical flow of cold, deep water towards the surface  High primary productivity and lucrative fisheries  Also occurs where strong winds blow away from, or parallel to, coastlines  Downwellings = oxygen-rich water sinks where surface currents come together

35. Seafloor topography can be rugged and complex  The seafloor consists of…  Underwater volcanoes  Steep canyons  Mountain range The planet’s longest range is under water  Mounds of debris  Trenches  Some flat areas

36. A stylized bathymetric profile of the ocean