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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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• Imagine life without water. Impossible! People, animals, plants - we all need water to survive !
• Water is used to produce the food we eat and the products we use. For example, manufacturing a car uses hundreds of thousands of litres of water.
• We flush a third of the water we use down the toilet. In the summer, watering our gardens can cause household use to jump 30%.
• Summer water use in Eagle Cliff dropped 70% when household meters were installed. When we have to pay for what we use, we tend to use less. Meters also identify leaks in the pipe system.

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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.

• When it hasn't rained for weeks, where can the water be coming from?
• How can we have water shortages when we get so much rain?

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.

• Our forests, streams, lakes, and wetlands provide an amazing service to us, clean water! They have evolved over millions of years of 'research and development'. Forests act as a giant filter. Rain infiltrates the porous organic soils and percolates slowly to streams where it is gradually released as clear water. As a result, forest streams commonly run clear even during storms.
• Wetlands, swamps, marshes, bogs, and fens provide many services. They filter stream waters, store water, and offer critical habitat for many plants and animals. Wetlands fill with water during rains and slowly release water through droughts. Before we understood their critical role, we used to ditch and drain wetlands to create lawns, pastures, or farms.
• Stream 'tornadoes' - In contrast to forests, rain does not easily infiltrate bare mineral soils exposed in disturbed areas. Instead, rainwater flows on the surface, eroding and carrying away fine sediment. During storms, streams flood quickly with muddy waters, eroding banks and filling channels with sediment. Such floods are like a tornado, wreaking havoc to stream life.
• A little mud never hurt anyone - or did it? Muddy water or turbidity is a major water contaminant on Bowen Island. Turbidity plays havoc with water treatment systems, reducing the ability of chlorine to disinfect. Muddy water also degrades stream gravel. The spaces in clean gravels are home to all kinds of life: fish eggs, insects, and even small fish. Silt clogs these pore spaces, reducing life in the stream.
• Are ditches a part of stream systems? You bet! Construction of ditches have added many miles to our stream system. Many small streams drain into ditches, and most ditches drain back into streams. So whatever goes into ditches, ends up in our streams!

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Forested corridors: vital to stream health

• Maintaining forest corridors along our streams is essential to stream health. Forests filter water, provide shade to cool waters during summer heat, provide logs that create pools and riffles, and provide wildlife travel corridors and habitat. They also provide walking trails for us!
• Investing in greenways: Bowen Island's green infrastructure is in good condition. We invest in it by protecting it as parkland. Over the last several years, Bowen Island Municipality has negotiated green infrastructure protection with landowners seeking to develop their lands. A network of greenways has protected streams, wetlands, and lakes in the Josephine Lake area. By protecting our land we protect our water !

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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

• Any body of rock or sediment that yields useful amounts of water is an aquifer. Bowen Island has two types of aquifer: fractured rock, and sand and gravel layers. The amount of water stored in fractured rock is typically limited, and these aquifers can run low during the summer drought. Sand and gravel can store more water and these aquifers are less likely to dry up in the summer. Shallow- dug wells can dry up as the water table falls during the summer.
• Groundwater flows from upland recharge areas to valley discharge areas
• Most recharging of aquifers occurs in forested uplands and valley slopes, but land clearing, road building, and ditching reduce water infiltration by creating impermeable surfaces and diverting water into ditches and streams. Infiltration ponds along ditches can increase the return of water into the groundwater system.

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Excessive pumping can reduce flow in streams

Oops! I dried up the stream

• Groundwater springs feed streams year-round. They are the only source of stream water during the dry season. A pumped well draws down the nearby water table. Excessive pumping for an extended period of time can lower the water table over a broad area. This can divert groundwater from streams and even cause streams to dry up. Nothing damages a stream like taking away its water!

Are we depleting our groundwater?

• To determine whether we are overpumping our island aquifers, we need a series of groundwater observation wells on Bowen Island. These are unused wells where water table levels can be regularly checked to determine long-term trends. Some groundwater monitoring has started on Bowen Island, but more observation wells are needed.

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.

• We can learn from past mistakes. Turbidity is a problem for many water systems. Its source is road construction, land clearing, and poor storm-water management. Failed septic systems and poor livestock practices can lead to bacterial contamination. Leaks from buried fuel tanks, fuel spills, and illegal burn piles have locally contaminated groundwater. We should also be concerned about risks from herbicides and pesticides.
• Septic fields are safe, economical, low-maintenance facilities for sewage disposal on Bowen Island, but they do need an annual check. Waste water flows into a tank where solids are trapped and bacteria break down wastes. Liquids flow into the drain field and percolate into the soil. Soil bacteria purify the effluent, producing clean water that becomes groundwater.
• Septic fields fail when drain fields clog and septic effluent rises to the surface and flows overland, contaminating wells and streams. Wells downhill from a failing septic field are only protected if they are capped and grouted properly. Otherwise, septic effluent can enter a well from the surface.

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?

• So our neighbours and ourselves don't run short. So we don't deplete our groundwater storage. So stream, lake, and wetland water levels aren't lowered unnecessarily, damaging their ecosystems. Because it saves us money. Because being wasteful is irresponsible.
• An average house roof on Bowen Island (125 square metres) will yield 160 000 litres or 35 000 gallons of water a year. Many homes on Bowen Island store rainwater in cisterns or tanks for use in the garden. Some even use rainwater for all their needs.
• Installing a water meter is the fastest way to detect leaks. A leaking toilet can waste 400 litres (90 gallons) a day.
• Outdoor water use, primarily gardening, increases Vancouver's water use by 30% during the summer. Lawns are incredibly thirsty, using four times as much as anything else in the garden, but this need not be. There are many beautiful gardens of native, drought-tolerant plants. Sprinklers can be replaced by efficient drip systems.
• Treating water to meet drinking water standards can be very expensive. Yet only 10% of our average household water use requires potable water for drinking, food preparation, and kitchen washing. We use this expensive treated water to flush toilets, water our gardens, wash the car, even fight fires!
• Most water used by households with septic fields returns to the groundwater system. We use the water, but we return it to the earth. This is good management. In contrast, sewer systems export water to the ocean, depleting groundwater storage.

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