I. Water Usage:

1. I. Water Usage: D. Water use sectors and various other factors affecting water use

2. Objectives: • List and describe a variety of water use sectors. • List and describe a variety of factors that affect water use.

3. Water use sectors: • Agriculture • Steam electricity generation • Cities, towns, communities • Manufacturing • Natural systems • Navigation • Hydroelectric power generation • Recreation

4. Agriculture: • Adequate, good quality water is essential for productive agriculture. • Irrigation water requirements are seasonal, and climate related. • Irrigation is now necessary in areas where rainfall was previously considered adequate (desertification).

5. Electricity generation: • Water can be used to pro- duce steam for electricity generation. • Water can also be used as a coolant for electricity generation. • Heated water can affect receiving bodies of water adversely or positively. • Hydroelectric power generation requires damming of rivers

6. Cities, towns, communities: • Domestic uses of water include: • drinking, • cooking, • sanitation, • lawn irrigation, • swimming pools, • cleaning, • fire fighting, etc.

7. Manufacturing: • While the efficiency of water use in manufacturing is increasing, • the consumptive use of water by manufacturing will continue to increase into the forseeable future. • Cost and availability are contributing factors in water use by manufacturing.

8. Natural systems: • Adequate quality water is essential to global ecosystems: • Marshes, • Wetlands, • Coastal esturine areas, • Unfortunately, goals of water use sectors may conflict with natural systems.

9. Navigation and recreation: • Navigation - adequate levels of water for lakes, rivers may be affected by water usage (e.g., dams may restrict river navigation). • Recreation - Swimming, boating, fishing, water skiing, ice skating, etc. are important recreational activities related to water availability.

10. Factors affecting water use: • Population • Desalination • Environmental protection, conservation, and management practices. • Cost of water • Water availability

11. Population: • Increasing population leads to increased water usage. • Water shortages almost always occur in areas of high population density. • Other factors such as water availability in these areas can contribute to water shortages.

12. Desalination: • Limited source of freshwater • Conversion of seawater (TDS 35,000 mg/l) or brackish water (TDS 3,000 - 35,000 mg/l) to fresh water (TDS 500-1000 mg/l) • Partial removal of some heavy metals.

13. Desalination, purification methods: • Distillation - heating of water to steam and recapture of condensed water. • Ion exchange - resins exchange ions. • Reverse osmosis - water movement through differentially permeable membrane by hydrostatic pressure. • Electrodialysis - Selected ions filtered out by membranes. • Ultrafiltration/microfiltration

14. Cost of Water • Conventional: $0.99-1.69 • Reverse Osmosis • Tampa Bay Water • (Seawater: $1.71-2.11, 35 mgd) • Ultrafiltration and RO (cost for treating brackish water is about the same as for conventional)

15. Environmental water protection, conservation and management: • Changing attitudes as to how water resources should be viewed are changing regulations. • Water conservation becoming more prevalent as cost increases and availability decreases. • Management practices can seriously affect the ways water is used.

16. Cost of water: • Most water is relatively inexpensive. • Government subsidies can reduce cost of water to farmers from an actual cost of $160/acre ft. to $3.50/acre ft. • Water costs will certainly increase dramatically as future supplies decrease.

17. Availability of water: • There is a balance of how much water is available (supply) versus the demand for the water by water use sectors. • As supply decreases, cost increases. • Demand can be decreased by proper conservation and management practices. • Environmental protection should be taken into consideration as a water use.

18. Summary: • There are a variety of water use sectors, including agriculture, industry, municipal, recreational, natural, etc. • How much water is used by each sector is determined by the availability of water, its cost, and consumer attitudes. • Ecosystems recycle, purify, and utilize water to maintain the environment.