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

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

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

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

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

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

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

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

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

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

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

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

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

Cost of Water l Conventional: $ l Reverse Osmosis –Tampa Bay Water u (Seawater: $ , 35 mgd) l Ultrafiltration and RO (cost for treating brackish water is about the same as for conventional)

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

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

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

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