Module 2: Water Use and Conservation

Transcription

1 Module 2: Water Use and Conservation Changes in Urban Streams Water Reuse Household Water Use Local Issues with Water Supply Conservation Opportunities Water Use Regulations Robert Pitt Department of Civil and Environmental Engineering University of Alabama Tuscaloosa, Alabama Long Island barrier island development, NY Moscow, Russia, fountains and kids in urban water Barton Springs, Austin, TX Navasink River, NJ River Walk, Austin, TX Dangers of urban waters are well known Confluence Park, Platte River and Cherry Creek, Denver, CO But.. stormwater can be considered a valuable resource in many situations. 1

2 Kitazawa Stream, Tokyo Kitazawa Stream is an example of a severely degraded urban stream in Tokyo that has undergone extensive modification. The stream watershed is 10.5 km 2 and has a population of about 150,000 people. The rapid urbanization in Tokyo since the 1950s has resulted in a severe decrease in groundwater infiltration during rains. This has caused decreased groundwater levels and decreased the associated natural recharge into urban streams. By the 1960s, there was almost no natural flow in Kitazawa Stream during dry weather. The only flows present in the stream was wastewater from homes. The stream was therefore of extremely poor quality, creating an unsafe and nuisance condition. In addition, the increased development caused frequent flooding. The local government authority therefore diverted the stream into an underground culvert. The aboveground area was converted into a promenade with extensive plantings. Recently however, local residents have requested the addition of a steam along the promenade. A very small flow (0.02 m 3 /s) of treated wastewater has been pumped from 11 km away to create this new stream (a two-storied watercourse ). The following shows the changes that Kitazawa Stream has undergone as the watershed has developed. This new steam, however small, has created a very important element in the lives of the residents of this heavily urbanized city. Special community organizations have been established to plan and manage the area. The history of Kitazawa Stream, Tokyo suburb (Fujita 1998) The history of Kitazawa Stream, Tokyo suburb (Fujita 1998) 2

3 The history of Kitazawa Stream, Tokyo suburb (Fujita 1998) The history of Kitazawa Stream, Tokyo suburb (Fujita 1998) Class AA A B C Distribution of Maryland Residential Water Use and Required Quality (Mallory 1973) Use Consumption by humans, food preparation, general kitchen use Bathing, laundering, auto washing Lawn irrigation Toilet flushing Rate of Use (gal/person/day) gal/day/acre 24.0 Percentage of Total Water Use Maximum Concentrations Allowed by Maryland for Different Reuse Categories, Compared to Typical Residential Stormwater Runoff (Mallory 1973) Constituent (mg/l) AA A B C Typical average residential stormwater quality and highest use without treatment Total solids Suspended solids Turbidity (NTU) Color (color units) ph (ph units) Oxygen, dissolved (minimum) Total coliform bacteria (MPN/100 ml) (A) 50 (none) 25 (none) 25 (B) 6 to 9 (AA) Near saturation (AA) >10,000 (none) 3

4 California Reuse Guidelines (Metcalf and Eddy 1991) Use of reclaimed water As shown on these tables, residential area stormwater can be used to meet at least class Landscaped areas: golf required 23 A water needs, except for suspended solids, courses, cemeteries, freeways turbidity, color, and coliform bacteria. The Landscaped areas: required 2.2 solids, turbidity and color levels are likely to parks, playgrounds, schoolyards be adequately reduced through storage and Recreational required 23 associated settling, plus possible post-settling impoundments: no public contact filtration. The most serious impediment for the Recreational required 2.2 reuse of stormwater in residential areas is the impoundments: boating and fishing only bacteria levels. Recreational required 2.2 impoundments: body contact (bathing) Secondary treatment and disinfection Secondary treatment, coagulation, filtration, and disinfection Total coliform bacteria criteria (MPN/100 ml, median of daily observations) Metcalf and Eddy (1991) state that primary treatment (similar to settling in a storage tank) reduces fecal coliform bacteria by less than 10%, whereas trickling filtration (without disinfection) can reduce fecal coliform levels by 85 to 99%. Chemical disinfection is usually required to reduce pathogen levels by 99.9+%, as likely needed to meet the above bacteria criteria for even the most basic water uses. Because of the risks associated with potential pathogens, reuse of stormwater in residential areas should only be considered where consumption and contact is minimized, restricting onsite reuse to classifications B and C, and only after adequate disinfection and site specific study to ensure acceptable risks. To further minimize risks, only the best quality stormwater (from a pathogen perspective) should be considered for reuse, such as roof runoff. It is possible to determine the likelihood of supplying needed irrigation water and toilet flushing water (reuse classifications B and C) from the stormwater generated from roof runoff by conducting an urban water budget. This budget requires a knowledge of all water sources and uses, and the associated quality requirements. 4

5 Available Freshwater Resources Small Fraction of all Water 5

6 Typical US Water Use (gallons/person/day) 6

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13 Water Regulations and Conflicts Water flows uphill towards money. Old western US saying Whiskey s for drinking water s for fighting about. Mark Twain Riparian water law is a common-law idea Owner of land has the right to withdraw water that is adjacent to the land. Water must be returned in a relatively unpolluted condition to ensure that downstream users do not have their water rights violated. The water must be used on land adjacent to the water source, not exported (reasonable use doctrine now allows irrigation). Evolved through practical use. Practiced mostly east of the Mississippi River where sufficient water resulted in few conflicts. Appropriation water law adopted from Roman civil law Owners of land may be denied the right to withdraw water if a more beneficial use is found. Government agencies appropriate the water. Water right can be taken away if better use found, or lost if abandoned. Water can be used away from the source. Common in western states where water is much more scarce. Increasing Recognition of Water Rights to Protect the Natural Environment Loss of fisheries, wetlands, lakes, and other ecological assets are shifting the balance of power governing water use, away from agriculture and towards protecting the natural environment. Australia s Murray-Darling river basin states have agreed to allocate 25% of the river s natural flow to maintaining ecological health in the system. 10% of the water from the Central Valley Project in California is to go for maintaining fish and wildlife habitat. 13

14 34 Countries in Africa, Asia and the Middle East are Classified as Water-Stressed Occurs when a country s renewable water supplies drop below about 1,700 m 3 per person. At this level, it becomes difficult for a country to collect enough water to satisfy all the food, household, and industrial needs of the population. These countries then begin to import grain (requires about 1,000 tons of water to produce a ton of grain). Poor countries have the vast majority of the water-stressed populations and they can ill afford imported grains. 14

15 About 40% of the World s Population live in Water Basins Shared by more than two Countries Biggest potential problems in Middle East: Jordan River (Israel, Jordan, Syria, and Lebanon) Nile River (Egypt, Sudan, Ethiopia, Zaire, Uganda, Tanzania, Burundi, Eritrea, Kenya) Tigris-Euphrates Rivers (Iraq, Syria, and Turkey) King Hussein declared in 1990 that water was the only issue that could take him to war with Israel 15

16 The national security of Egypt is in the hands of the eight other African countries in the Nile basin. Saudi Arabia uses Fossil Groundwater for 40% of their needs Groundwater depletion more than 5 billion cubic meters per year and rapidly growing. Boutros Boutros-Gali, when he was Egypt s Minister of State for Foreign Affairs Water Issues Increasingly Responsible for Armed Conflict Dispute over the headwaters of the Jordan River helped spark the 1967 Arab-Israeli war. Bypass canal project in southern Sudan one factor in continuing civil war. Current Serious Water Conflicts Israel s unrestricted use of groundwater from the Jordan River basin in occupied territories. Egypt-Sudan agreement totally allocates Nile River downstream flow without reference to upstream needs. Construction of dams in Turkey reduce Euphrates water to Iraq to as little as 10% of normal flow, and to 60% for Syria. 16

17 More than 2,000 International Treaties Relating to Common Water Basins Common basins make up 60% of the land in Africa and South America US and Canada Great Lakes Compact The Nile Water Agreement (Egypt and Sudan) India and Pakistan share development of the Indus River. India and Bangladesh agree to maintain minimal flows in the Ganges. US and Mexico agree on flow conditions in Colorado and Rio Grande Rivers. Argentina and Brazil agree on management of the Paraná River. Gonick and Outwater. The Cartoon Guide to the Environment. Formula for Survival A decade ago, a fish Malthusian might have predicted the end of salmon as a food. Human ingenuity seems to have beaten nature once again. Forbes 1990 (Population) X (Demand) must be <1 (Sustainable Supply) Malthus Bailey, Earth Report

18 Environmental Trends Shaping the New Century Population growth Rising temperature Falling water tables Shrinking cropland per person Collapsing fisheries Shrinking forests Loss of plant and animal species State of the World 2000 Time and Scale of Environmental Concerns (Graedel) Problems in Our Future (recovery periods for individual actions) Water Supply and Water Quality Short Term (< 100 years): Tree falls Land slides Oil spills Slash and burn Forest fires Floods Tsunamis Volcano eruption Acid rain Long-Term (>100 years): Heavy metal deposition Groundwater exploitation Ozone depletion Meteor strike Climate change Conservation easiest to develop and cheapest new water source Water quality problems becoming better understood Habitat destruction becoming recognized as serious issue 18

19 Development or Reservation? Development: Atmospheric nitrogen, electric steel, cement, marble, brick, lime, iron, coal, fruit, lumber, and cotton. 300,000 horsepower Coosa-AL navigation = 10 railroads Reservation: Falling, wasting as I flow. A mighty brimming river. My commerce tied, my strength untried. Fix me now or never. Nearly the entire spectrum of conservation and efficiency options cost less than the development of new water sources. Sandra Postel 1996 W.P. Lay. River Problems of Alabama Estimated Costs of Water Management Options Reducing demand through conservation/efficiency Treatment and reuse of wastewater for irrigation Desalination of brackish water Development of marginal water Desalination of seawater Estimated cost range (cents/m 3 ) In El Paso, pricing and educational efforts are credited with a substantial reduction in water use. Conservation meets about 15 to 17% of the city s future water needs. Besides slowing the rate of depletion of the groundwater supply, the conservation measures cost about 8% less than the cost of existing water supplies (about $135 per 1,000 m 3 ). World Bank

20 John Boland, Johns Hopkins University, Abel Wolman Lecturer WorldWater, January 2003 WorldWater, January 2003 WorldWater, January 2003 Hydroplus, July

21 Hydroplus, July 2003 Hydroplus, July 2003 Homework Problem Nature has no reset button State of the World 2000 Determine the water use in your household, by category, for a 5 day period. Identify the water classification for each category, and sum the total water needs by category. How can conservation and/or reuse reduce your household water needs? What secondary benefits may occur with reduced water supply needs and associated decreased wastewater discharges? 21