Distribution of Water

2. Distribution of Water 97.2% of Earth’s water is not potable (ocean water) 2.1% of Earth’s water is frozen in polar regions That leaves only 0.7% in liquid, salt-free, fresh water for drinking purposes In streams, river, lake, pond, puddle, and in soil and rock The % of Earth’s water that is in different environments varies little with time

3. Sources of Earth’s waterAnimation

4. Distribution of Water … Consumption of this limited source of water increases with population In year 1900, people consumed ~141 cubic miles per year Today we use about 1000 cubic miles of water per year Consumption doubles every 20 years. 80 countries, with 40% of Earth’s population, have chronic water shortage 150 out of 214 largest river systems are shared by two countries 50 rivers are shared by 3 to 10 countries Thus, water will be the dominant international issue for wars in the coming years

5. Water on Earth’s Surface Each year, more water precipitates (~22,600 mi3) on land than evaporate (14,000 mi3) from it The remaining 8600 mi3 is the water which is available to us, which drains back into ocean Part of this available water enters streams or lakes and constitute the surface water The rest infiltrate the soil and rock (by gravity), and become stored as groundwater Groundwater generally remains out of sight, but may resurface as springs Availability of surface water is: precipitation - evaporation - surface runoff - infiltration

10. Hydrologic Cycle Cyclic movement of water: From the air to the ground, to streams, to the ocean, and back to the air Humans interfere with the cycle by: ponding water in reservoirs behind dams removing water from underground faster than it can be replenished changing the climate through global warming The cycle interconnects Earth’s water, air, soil, rock, and living things

11. Hydrologic cycle The hydrologic cycle is a summary of the circulation of Earth’s water supply Processes involved in the hydrologic cycle Precipitation Evaporation Infiltration Runoff Transpiration

12. The Hydrologic CycleAnimation

15. Hydrologic Cycle Even though the distribution of water on Earth is almost constant with time: Water molecules continuously shift location on Earth Water evaporates from the top of the surface waters and land to become vapor The vapor is then precipitated back (rain, snow, etc) to the surface of land and ocean The precipitated water partly: runs off on the surface to form surface waters infiltrates into the ground to make groundwater evaporates back into the atmosphere

16. Infiltration Animation

18. Fresh water of the Hydrosphere

31. Interactions between surface and ground waters (SW &GW) Overdraft of GW: Leads to lower water levels of streams, lakes, reservoirs, etc. Overuse of SW: Yields lower discharge rates of GW Effluent (Gaining) stream (in GW discharge zone): Tends to be Perennial (i.e., flow all year) Influent (Losing) stream (in GW recharge zone above the water table): Are often above the water table, and flow in direct response to precipitation May be intermittent or ephemeral (flow part of the year) Special linkage area: Sinkholes and cavern systems in the karst terrains

32. Water Use (1) Offstream use: Removal or diversion from its SW or GW sources temporarily e.g., water for irrigation, thermoelectric, industrial use Consumptive use: Type of offstream use of water without water returning to the SW or GW e.g., water incorporated into crops/products; transpiration and human use Instream use: Water is not withdrawn from its source e.g., water for navigation, hydroelectric power generation, fish and wildlife habitat, recreational uses

38. Water Management (2) New philosophy of water management based on geologic, geographic, climatic, economic, social and polotical factors Philosophy from Luna Leopold – a leader in study of rivers and water resources Strategies More SW use in wet years, more GW use in dry years Reuse and recycle water regular basis as well as emergencies