Chapter 1: Introduction • 1

Chapter 1

Introduction

Whatever other views astronauts maysee, Earth will appear as a mainly blueand white planet set against thebackdrop of the blackness of space andwith the relatively small areas of thecontinents visible in shades of green,grey and yellow. The white areas are clouds of water vapour in theatmosphere, and the blue areas arebodies of surface water mainly in theform of seas and oceans. Most of theblue surrounds the continents andillustrates the first difficulty of watersupply - over 95 percent of the water inthe world is saline.

The water cycle is the most crucial partof the hydrological cycle, and the basisfor all human life on the planet (Figure1.1). Water is evaporated from the seasby the heat of the sun - leaving the saltbehind. The clouds of water vapourthus formed are blown through theatmosphere by winds until part of thewater falls on land as rain or snow.The rain or melt water seeps into theground or runs off as surface water instreams and rivers. Rather significantly,this small proportion of total watermakes life possible on Earth. Peopleintervene in the water cycle to makeuse of surface water and groundwater,almost invariably polluting it in someway before returning it to the sea -either by discharge into rivers or bydirect outfalls.

The interdependence and continuousmovement of all forms of water providethe basis of the concept of the

hydrological cycle. Water vapour in theatmosphere condenses and gives rise toprecipitation. In the terrestrial portionof the cycle only a proportion of thisprecipitation will reach the groundsurface because of interception byvegetation, buildings, roads and otherforms of construction. From here it isevaporated back to the atmosphere.Once the precipitation reaches theground surface it may take one of three courses, viz. into storage,overland flow or through flow.

The water may remain as surfacestorage in the form of pools, puddlesand surface moisture that areeventually evaporated and return waterto the atmosphere. Water may alsoremain in storage for a period of timeand then follow one of the othercourses, for example, water may flowout of a storage pool or be drawn intothe soil.

If the soil or rock is at saturation pointor impermeable in nature, the potentialfor water to percolate into the landmass is strictly limited. Overland flowwill occur over the surface of theground and collect as surface storage inponds and lakes or as runoff into theseas or oceans. From these bodies ofwater it may be evaporated back to the atmosphere or be drawn into the surrounding soil to collect asgroundwater.

Precipitation may also infiltrate throughthe ground surface as through flow to

join existing resources of soil moisture,from where it may move to one ofthree areas. Firstly, it may be extractedfrom the soil by evapo-transpirationand released into the atmosphere.Secondly, it may move by further sub-surface through flow into riversand streams, and be deposited into theoceans or evaporated back to theatmosphere. Thirdly, it may seepdown into the groundwater reserveswhere it may be held for weeks,months, and years or even longer.Rivers, streams and lakes are used asabstraction points for water (Figure1.2). If lakes are used, abstractionshould not be at a rate that mayendanger the integrity of the lake.

Abstraction should always be at asustainable level in order to avoidadverse effects on the local ecosystemand on the people that may dependupon it. Abstraction from rivers andstreams should also be at levels that aresustainable – that may follow naturalrates of recharge. It may be necessaryto construct a reservoir in order toensure that seasonal variation in flowdoes not adversely affect supply. As rivers and streams are vulnerable topollution, a reservoir can offer thepotential to close intakes until thepollutant has passed whilst stillmaintaining supplies. If contaminatedwater enters the reservoir the storedvolume of water would effectively

Figure 1.1 Schematic illustration of the water cycle.

Atmosphericvapour storage

Precipitation

Rain

Interception storage

Surface waterchannel

LakeOcean

E/T

GW

E/T

E

E

E

Snow

SnowSnow melt

Soil storage

Aquifer storageE = EvaporationE/T = Evapo-transpirationGW = Groundwater

Figure 1.2 Surface water use in a river catchment.

Snow melt

Catchwatercanal

Compensation flowand regulation

release

Net yieldto supply

Water treatment

Pumped reservoirsSewage

treatment

Directsupply

reservoir

Direct riversupply

Screenedsea outfall

Sea

Storagereservoirs

Rainfall

Boreholesupply

Regulatingreservoir

Aquifer

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Chapter 1: Introduction • 3

dilute the pollutant.

Springs occur where the naturalgeology of an area causes groundwaterto well up and flow as surface flow.Groundwater can be considered as allwater flowing through or stored inrocks and soil strata, and it representsthe largest accessible store of freshwater on Earth. Wells and boreholesare extensively used worldwide to extract groundwater and, in theindustrialised countries, many aquifersare being depleted by over-abstraction.There are much smaller sources ofwater that can be exploited, forexample, rain water falling on to abuilding - that may be collected andstored for future use. In some cases asystem of roof drainage channels isused to collect the water and to moveit into store. In small communities in developing countries improvisedarrangements with plastic sheet, forexample, can sometimes be used to harvest water during rainstorms toaugment supplies during the dry

season. Management of dry seasonsupplies is an important aspect for all communities, notwithstanding thelevels of industrialisation or thesophistication of the delivery systemsinvolved (Figure 1.3).

Expanding populations worldwiderequire more water both for personalconsumption and for producing theextra food required. Ironically, manynew high yielding crop varieties needmuch more water than older varietieson a weight for weight basis. Similarly,new food processing facilities canmake considerable supply demands in areas which may not have adequatesupply infrastructure, sufficientcatchment area or aquifer capacity. On every continent industrialisation,intensive agriculture and otherdevelopments are degrading thecatchments of major rivers, andadversely affecting the quantity andquality of surface water run-off. In anumber of countries, including China,the development of large areas of land

Figure 1.3 River Thames at Hampton Court, England. Not all water shortages are experiencedin the traditionally dry countries. In 1976, drought in SE England caused the river tocease to flow. Pumping water back over the weir from downstream was necessary,to feed water treatment works and to maintain water supplies to London.

is compromised by the availability ofwater. Together with droughtsexperienced in recent years thesefactors have led to many countriessuffering shortages and, as is so oftenthe case, with the poorest people in thecommunity usually the most seriousaffected. Sustainable life requires, atthe very least, 20 litres per head perday – before people are at risk. Accessto a safe water supply is fundamentalto good health, and water bornediseases are the single largest cause ofillness on the planet. The non-government organization (NGO) WaterAid of the United Kingdom estimatedchild mortality at 25 000 deaths per dayin what has been referred to as “ the silent genocide” (Water Aid, 1995).

Will there be ‘Water Wars’, i.e. warsover access to water? It is the essentialneed for water that gives it such aprimary strategic significance. IsmailSerageldin of the World Bank repeatedthe then UN Secretary General BoutrosBoutros Ghali’s assertion that the nextwar in the Middle East would be foughtover the waters of the River Nile (Vidal,1995). He maintained that 85 countrieshave water shortages that affect health and hold back commercialdevelopment. More than two billionpeople do have not have access toclean water and sanitation, andwordwide demand for water isdoubling every 20 years. Supply isbeing totally outstripped by increasingdemand, and the situation in much ofthe Middle East and Africa remainsprecarious. Several of the greatestrivers in the world including the Nile,Mekong, Indus and Niger flow throughmore than one country. Almost everycountry has need for extracting asmuch water as possible, and thepotential for tension to upset thepolitical balance in these regions isimmense. Demand is certain tooutstrip supply. It is suggested that theper capita water use in Egypt will need

to drop by 30 percent and that inKenya by 50 percent in less than 10years to provide for security of supply.Serageldin has said that the amount ofwater available to each person in theMiddle East will drop by an estimated80 percent in a single lifetime.

The World Bank sees the solution towater supply needs as a market place issue, with private companiesproviding a vital – commercial –service. If this is to be the case thenthe ability to pay may be extremelydifficult to reconcile in the poorestcountries, and the methods by whichpayment is determined need to beflexible to allow for flexibility of application. To be wrong couldquickly be fatal. Vidal (1995) quotedthe words of Water Aid:

“.... but going down the route of privatefacilities may not be appropriate. Thereare other ways. Otherwise water has afunny way of ending up only in the richman’s bucket these days”.

But what if the rich man is a tourist?Tourism is viewed as a ripe area for expansion in many developingcountries but, unfortunately, it canexert an extremely high per capitawater demand. Take, for example, thedaily personal use allocation fortourists in one Mediterranean hotel - at500 litres per head. On this basis thewater sufficient for 100 rural familiesfor three years will serve 100 luxury hotel guests for just 55 days. Invarious countries, hotel and tourismdevelopments have had a dramaticimpact on the availability of water, withcompanies buying up or placing adisproportionate demand on raw watersources. The imbalance in the system between investments requiredfor tourist infrastructure and those

for domestic communities is moreinnocuous where golf courses areinvolved; grass swards kept green year

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Chapter 1: Introduction • 5

round within sight of people who areshort of water.

There are a number of problemsassociated with providing a safe watersupply. In major urban conurbationsincreasing demand is an importantfactor in determining pumpingpressures and shortening the life ofmain pipe networks that are old,although demand itself is not asobvious as it sounds. “Personal” usefor drinking, washing, preparing food,showers, baths and toilets is typically150-200 litres per person per day innorth-western Europe, but there aremany “hidden” uses of water. A supplyof plastic wrappers for a week, forexample, has an associated annualwater demand of say 85 000 litres; adrink bottling and canning plantrequires 110 000 litres/annum; and adaily newspaper requires more than250 000 litres/annum. Industrial use ofwater is high and expanding fast.

In most countries, it can be argued thatthe true value of water is not reflectedin the price to the consumer. In theUnited Kingdom, for example, this canbe expressed as US$1 per tonnedelivered to the front door for a commodity which - if not availablefor six days - can be life-threatening.The effectiveness of investing in a safewater supply is graphically illustratedby events in Peru in 1991-92, wherethree months of a cholera epidemic -the classic water borne disease - costthe country an estimated one billion USdollars. This was three times the totalamount invested by Peru in providinga safe water supply infrastructureduring the decade 1980-90.Consultants and contractors competeinternationally for the larger water andwastewater projects, with operationalexpertise traded for the application anduse of systems of supply, treatment anddistribution that may require the use ofsophisticated technologies.

Funded by capital loans and othermajor sources of finance such schemestypically address the needs of majorcities, although few solutions havebeen found to the problems of therapidly increasing numbers of peri-urban poor. There is a clear need for simple and robust low technologytreatment systems for use in thecountless small communities of thedeveloping world. Inappropriate watertreatment technologies are oftenexported by companies from theindustrialised countries, and thenquickly fall into disrepair from want of the technical and/or the financialeffort required to maintain them. Insmall rural communities appropriatewater treatment, water supply,wastewater collection, wastewatertreatment or human waste disposalsystems are required. This will helpimprove health and sanitation in thecommunity, and enhance agriculturaland agro-industrial production and thesocio-economic development of thepeople concerned.

The introduction of planning controlsfor commercial, environmental,agricultural and other developments is essential for the growth ofsustainable communities in areaswhere river catchments are sensitive toincreased demands for water. In manydeveloping countries river catchmentsare neither gauged nor monitored for water quality. In such cases theintegrated use of remote surveillanceor aerial surveys, land surveys,hydrological surveys, geographicinformation systems and water qualitysurveys can support the developmentof sectoral planning tools.