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Natural Resources Canada > Waterscape Bowen Island
W v. 12.00 GlobalMapper (2010 r.) wprowadzono funkcję analizy zlewni wód - (watershed). Poszukując w sieci istniejących opracowań dot. tego tematu dotarliśmy na powyżej zlinkowaną stronę omawiającą w prosty i bardzo poglądowy sposób zagadnienia związane zarówno z tematem zlewni wód, a także z ochroną wód powierzchniowych. Pustynnienie kontynentów, zmiany klimatu i coraz bardziej odczuwalne niedobory - czystej, zdrowej wody pitnej - zmuszają rządy i jednostki terytorialne do analizy sytuacji i poszukiwania sposobów na ochronę istnejących zasobów, w tym także na określenie posiadanych rezerw i wprowadzenie bardziej gospodarnych sposobów wykorzystywania tego, czym jeszcze dysponujemy. Poziom merytoryczny tego materiału, sposób wizualizacji, jak również zakres omawianych zagadnień - poprostu nas urzekł. Zwróciliśmy się więc do pana
Dr. Bob Turner - Research Scientists, ESS/GSC-AWCB/GSC-PAC/VSDNatural Resources Canada625 Robson Street, 14 FloorVancouver, BC Canada V6B 5J3 z prośbą o zgodę na opublikowanie fragmentów tych materiałów w celach popularyzatorskich.
Wkrótce otrzymaliśmy następującą odpowiedź: "You are welcome to use the Bowen Island water information on your site, for the purpose of non-commercial sharing information with the public. Please include the website address of the material so that people are led back to our website if they want more information. - Good luck - Bob Turner"
Citation: Waterscape Bowen Island: water for our island community; Turner, R J W; Franklin, R G; Journeay, J M; Hocking, D; Franc de Ferriere, A; Chollat, A; Dunster, J; Whitehead, A; Whitehead, D G. Geological Survey of Canada, Miscellaneous Report 88, 2005;
Z radością przekazujemy więc wszystkim zainteresowanym powyższy link - zachęcając do zgłębiania tematu. Chciałoby się powiedzieć, że z pewnością pozytywnie zazdrościmy władzom Bowen Island tak mądrego, systematycznego i dogłębnego zajęcia się tym tematem. Być może przynajmniej niektóre z naszych samorządów przyjmą ten wzór jako przykład dobrego podejścia do tematu i obowiązujący standard.
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Bowen Island, Vancouver, Canada
Bowen Island, British Columbia, is an island municipality in Howe Sound, and within Metro Vancouver. Approximately 6 km wide by 12 km long, the island at its closest point is about 2 km west of the mainland. There is regular ferry service from Horseshoe Bay, as well as three water taxi services. There were 3,551 permanent residents as of the 2007 BC Stats Estimate, a number that is supplemented in the summer by roughly 1,500 visitors, as Bowen Island is a popular vacation home location for British Columbians. About 500 workers and over 200 students commute to offices and schools on the mainland each day. The island has a land area of 49.94 sq km (19.28 sq mi). Time zone: PST (UTC-8) / - Summer (DST) PDT (UTC-7); Postal Code V0N 1G0
Municipal Website: http://www.bimbc.ca/
Wikipedia: http://en.wikipedia.org/wiki/Bowen_Island
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Average daily water use per person (litres)
Where does all that water go?
It all falls from the sky !!!
Rainfall feeds Bowen Island's entire fresh water supply. Moisture from the Pacific Ocean is blown eastwards and falls as rain. Rainwater flows into streams to be carried quickly to the sea (perhaps with a pause in wetlands or lakes) or sinks into the ground to join the slow-moving groundwater system. Shallow groundwater returns to the surface as springs, adding flow to streams. The island's fresh groundwater is entirely surrounded by salty groundwater that underlies the seafloor. Some streams on Bowen Island flow year round, even through the summer dry season.
Because so much of our 1.5-1.8 m of annual rainfall comes during the winter and runs quickly to the sea. The land can't store enough of our winter rains, so water shortages occur during the summer dry season. Most rainwater returns to the atmosphere through plants and evaporation. Much of the rest is carried quickly to the sea by streams. Some stream water is stored for days to months in wetlands, ponds, lakes, and reservoirs. A small amount infiltrates the ground, evades capture by plant roots, and can be stored for months to centuries in the slow-moving groundwater system.
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Watersheds everywhere!
Watersheds everywhere!
All the land area that drains into a stream system is called a watershed. Most areas of Bowen Island drain into some stream, so it is likely that you live in a watershed. A water-supply watershed is the part of a watershed upstream of a water-supply intake. Many parts of Bowen Island are water-supply watershed areas. Do you live in one?
Living in our water-supply watersheds
Vancouver protects water quality in its watersheds by restricting access. Things are different on Bowen Island. Some water-supply watersheds lie within forested Crown Lands and are relatively pristine. But others, such as the Grafton Lake water supply, include residential and commercial areas, roads, and livestock. All of these uses represent potential sources of contamination. Should we be concerned?
Bottled water - the foreign invasion!
Bottled water has become very popular. While it seems safe and convenient, there are disadvantages: it's expensive, it creates waste containers, and trucking water generates air pollution, causing problems like asthma and global warming.
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The clean water factory: forests, streams, and wetlands.
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Forested corridors: vital to stream health
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Water stored underground: vital and vulnerable
Rainwater percolates into the earth. Soil and rock are like a giant sponge, full of holes - typically tiny pores and cracks just millimetres in size. Below the water table, these holes are full of water. This is groundwater. Groundwater slowly travels through connected pores and cracks just centimetres to metres per year.
Protecting the balance
Groundwater storage is like a bank account. The balance falls when withdrawals exceed deposits. Nature makes deposits through rainfall, and withdrawals through leakage of groundwater to streams and the ocean. Our wells represent further withdrawals. If total withdrawals exceed deposits, we deplete our groundwater storage. Do we know if we are draining our account?
Water table ups and downs through the seasons
The amount of water stored underground changes through the seasons. As winter and spring rains infiltrate the ground, stored groundwater increases and the water table rises. When the rains stop, the water table falls as groundwater leaks into streams and the ocean. Well pumping also removes water and lowers the water table. Excessive pumping of groundwater can result in long-term depletion of groundwater storage.
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Underground lakes and rivers
Not on Bowen Island. Large underground streams and lakes only occur in limestone cave systems. Limestone is unique as it dissolves in water, allowing caves to form. Bowen Island's granitic and volcanic rocks do not dissolve in water and so lack cave systems.
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Tapping into water stored underground
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Excessive pumping can reduce flow in streams
Oops! I dried up the stream
Are we depleting our groundwater?
Protecting water quality in source areas is our first line of defense. Beyond that, community water systems use disinfection (chlorination, ultraviolet radiation) to kill bacteria, viruses, and Giardia cysts, and filtration to remove turbidity that interferes with the sterilization process. Some homeowners on wells treat water to remove dissolved minerals such as calcium (hardness), iron, manganese, or arsenic.
Is your well protected?
Trouble occurs when contaminated surface water leaks down into wells. To prevent this, properly sealed wells have grout injected between the well casing (steel pipe in the upper well) and the well wall, and a cap is placed on the top of the casing; however, many wells are not properly sealed. Is yours?
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Why should we conserve water?
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