Dr. Shahida Rasheed

Three main sourcesRainSurface water:Impounding reservoirsRivers and streamsTanks, ponds and lakesGround water:Deep and shallow wellsSprings

WATER DISTRIBUTIONGlobally the total quantity of water available is fixed. It is distributed as: Fresh water (0.2%) & Sea water (99.8%)

ClassificationPotable waterClean waterPolluted waterContaminated water

SAFE & WHOLESOME WATERFree from pathogensFree from harmful chemical substancesPleasant to the taste, i.e. free from colour and odour andUsable for domestic purposes

Eutrophication: over nourishing of body stored water, by presence of phosphorous and nitrogen which helps in algal growth.Biomagnification: bioaccumulation of chemicals in aquatic life.Thermal stratification: warmer water in summers block oxygen from reaching the colder layer which causes accumulation of hydrogensulphide and carbondioxide.

Purification of water on a small scaleHOUSEHOLD LEVEL Boiling Bleaching powder Chlorine tablets Potassium permagnate Iodine Double pot method Ultraviolet radiation Filters (Berkefeld, Pasteur Chamberland and Katadyn)

Breakpoint ChlorinationAddition of Chlorine to Ammonia in water produces Chloramines. When further chlorine is added a reduction in the residual chlorine occurs. Upon continued addition a fall will occur to a level where the proportion is equal to the added chlorine. This point is known as Break Point Chlorination. It corresponds to superchlorination.

Hardness of water is defined as the soap destroying power of water. (mEq/L)Due to: Calcium bicarbonateMagnesium bicarbonateCalcium sulphateMagnesium sulphate

WATER QUALITY INDICATORSDissolved Oxygen (DO)Biological Oxygen Demand (BOD)pHColiform BacteriaHardness of water

Sampling of water Collection from tapCollection from rivers, lakes reservoirs and wellsTransport and storage samples

Quantity of water in a wellDeep Wells Shallow Wells Quantity of water in litres:square of diameter X depth of water X 800of well in meters in meters

square of diameter X depth of water X 5 of well in feet in feet