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Water Demand &Flow Calculations Lokhaze Ali Visiting FacultyNICE, SCEE, NUST
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Thought of the Day Water Demand & Flow Calculations 2
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Water UseWater use can be distinguished into threedifferent types1. Withdrawals or Abstractions2. Consumptive Water Use3. Non-Consumptive Water Use Water Demand & Flow Calculations 3
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Withdrawals or Abstractions• Where water is taken from a surface or groundwater source• after use returned to a natural water body• e.g. water used for cooling in industrial processes returned to a river• such return flows are important for downstream users Water Demand & Flow Calculations 4
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Consumptive Water Use• Water consumption that starts with a withdrawal or an abstraction but in this case without any return flow• water abstracted that is no longer available for use• it has evaporated, transpired, been incorporated into products and crops• consumed by man or livestock or otherwise removed from freshwater resources• e.g. water use include steam escaping into the atmosphere and water contained in final products i.e. it is water that is no longer available directly for subsequent uses Water Demand & Flow Calculations 5
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Non-Consumptive Water Use• Water withdrawn for use that is not consumed• e.g. water withdrawn for purposes such as hydropower generation• recreational activities• boating or fishing where the water is still available Water Demand & Flow Calculations 8
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Water demand• Volume of water requested by users to satisfy their needs• Often considered equal to water consumption• Conceptually the two terms do not have the same meaning• In rural parts of Pakistan, the theoretical water demand considerably exceeds the actual consumptive water use Water Demand & Flow Calculations 9
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The 4 S’s: Some Common Terms• Water Shortage - absolute shortage where levels of available water do not meet certain defined minimum requirements.• Water Scarcity - a more relative concept describing the relationship between demand for water and its availability.• Water Stress - the symptomatic consequence of scarcity which may manifest itself as increasing conflict over sectoral usage, a decline in service levels, crop failure, food insecurity etc..• Water Security - a situation of reliable and secure access to water over time.
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Water Scarcity Water scarcity category and Volume of water available associated problems (m3/person/year) Beyond the “water barrier”: continual, < 500 wide-scale water supply problems, becoming catastrophic during droughts. Chronic water scarcity: continual water 500 to 1,000supply problems, worse during annual dry seasons; frequent severe droughts. Water stressed: frequent seasonal water 1,000 to 1,666supply and quality problems, accentuated by occasional droughts. Moderate problems: occasional water 1666 to 10,000 supply and quality problems, with some adverse effects during severe droughts Well-watered: very infrequent water > 10,000supply and quality problems, except during extreme drought conditions. Demand & Flow Calculations Water 11
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Water Use• Agricultural use - Any use or • Residential use - The use of activity involving agriculture, water that is billed to single and including irrigation multi-family residences, which• Commercial use - The use of applies to indoor and outdoor water by a place of business, uses such as a hotel, restaurant, or office building. This does not include multi-family residences or agricultural, industrial, or institutional users• Industrial use - The use of water in processes designed to convert materials of a lower order of value into forms having greater usability and commercial value, and the development of power by means other than hydroelectric, but does not include agricultural use Water Demand & Flow Calculations 12
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Top 10 Freshwater Consumers Water Demand & Flow Calculations 13
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World Water Use by Sector Source: OECD Environmental Outlook Baseline, 2007 Water Demand & Flow Calculations 14
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Typical Water Use at Home Shower 2 gallons per minute Teeth brushing <1 gallon, especially if water is turned off while brushing Hands/face washing 1 gallon Dishwasher 4 to 10 gallons/load Dishwashing by hand 20 gallons Clothes washer 25 gallons/load Toilet flush 3 gallons Outdoor watering 5 to 10 gallons per minute Water Demand & Flow Calculations 15
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Residential Gallons Per Capita Per DayResidential gallons percapita per day =(Residential Use ÷Residential Population) ÷365• Residential Use = Single-Family Use + Multi-Family Use• Residential Population = theresidential population of theservice area. Includes onlysingle- and multi-familypopulations Water Demand & Flow Calculations 16
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Commercial Use Water Demand & Flow Calculations 17
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Water Data USGS Water Demand & Flow Calculations 18
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Water Demand US Water Demand & Flow Calculations 19
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Estimating Water Withdrawals for Livestock Wt = ((Pdc * Cdc) + (Pbc * Cbc) Plh = Number of laying hens; Clh = Coefficient for laying hens, in gallons + (Ph * Ch) + (Plh * Clh) + (Pbh * per day; Cbh) + (Pt * Ct) + (Ps * Cs) + (Pg Pbh = Number of broilers and other chickens; * Cg) + (Pe * Ce)) / 1,000,000 Cbh = Coefficient for broilers and other chickens, in gallons per day; where Pt = Number of turkeys; Wt = total water withdrawals, in million Ct = Coefficient for turkeys, in gallons per gallons per day; day; Pdc = Number of dairy cows; Ps = Number of sheep and lambs; Cdc = Coefficient for dairy cows, in Cs = Coefficient for sheep and lambs, in gallons per day; gallons per day; Pbc = Number of beef and other cattle; Pg = Number of goats; Cbc = Coefficient for beef and other Cg = Coefficient for goats, in gallons per day; cattle, in gallons per day; Pe = Number of horses, ponies, mules, burros, and donkeys; and Ph = Number of hogs and pigs; Ce = Coefficient for horses, ponies, mules, Ch = Coefficient for hogs and pigs, in burros, and donkeys, in gallons per day. gallons per day; Water Demand & Flow Calculations 20
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Water-use coefficients for Livestock Water Demand & Flow Calculations 21
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Different crops contribution to total water footprint of crop production Period: 1996–2005 Water Demand & Flow Calculations 22
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The Green, Blue, Grey and TotalWater Footprint of Crop Production Period 1996-2005 Water Demand & Flow Calculations 23
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Urban Water Demand in California to 2100 Case Study Water Demand & Flow Calculations 24
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Urban Water Use Water Demand & Flow Calculations 25
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Commercial & Industrial Water Use Water Demand & Flow Calculations 26
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Simple Linear Forecasts Water Demand & Flow Calculations 27
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Global Surface Warming & Population Projections Water Demand & Flow Calculations 28
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Time Series of Decadal AverageWater Use for Six Simulations Water Demand & Flow Calculations 29
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Simulated Urban Water Use underScenarios of Conservation and Population Water Demand & Flow Calculations 30
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Flow Calculations Water Demand & Flow Calculations 31
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Conversion Factors Multiply By To obtain gallon (gal) 3.785 liter (L) gallon (gal) 0.003785 cubic meter (m3) million gallons 3,785 cubic meter (m3) (Mgal) gallon per day 0.003785 cubic meter per (gal/d) day (m3/d) million gallons 0.04381 cubic meter perper day (Mgal/d) second (m3/s) Water Demand & Flow Calculations 32
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Flow CalculationsFlow is expressed in the English Flow Conversionssystem of measurements using Flow rates can be converted tomany terms. The most common different units using theterms are: conversion process. gpm - gallons per minute The most common flow conversions are: cfs - cubic feet per 1 cfs = 449 gpmsecond and gpd - Gallons per day 1 gpm = 1,440 gpd MGD - Million gallonsper day Water Demand & Flow Calculations 33
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Flow Calculationsgpd to MGD MGD to gpmTo convert gallons per day (gpd) to There are many instances whereMGD, divide the gpd by 1,000,000 the design or plant information isgallons or 106. given in MGD and we wish to have the flow in gpm. This conversion isFor example: accomplished in two steps.Convert 125,000 gpd to For Example:MGD. Convert 0.125 MGD to gpm125,000 gpd = 0.125 MGD Step 1) Convent to gpd by multiplying by 1,000,000Or 0.125 x 1,000,000 = 125,000 gpdconvert 2,300,000 gpd to Step 2) Convert to gpm by dividingMGD by the number of minutes in a day (1,440 min/day).2,300,000 gpd = 2.3 MGD 125,000 gpd = 86.8 or 87 gpm Water Demand & Flow Calculations 34
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Detention TimeDetention time is the Sample Calculationamount of time that a fluid The reservoir for the town isstays in a container. 85,000 gallons. The well will produce 55 gpm. What is theDetention time is expressed in units of time. detention time in the tank inThe most common are: seconds, minutes, hours.hours and days. Solution:Detention Time = Volume DT = 85,000 gallons = 1,545 min 55 gpm Flow Rate orFor example: 1,545 minutes = 25.8 hrs1) if the flow is in gpm then the detentiontime will be in minutes; 60 minutes/hror2) if the flow is in gpd, then the detentiontime will be in days. Water Demand & Flow Calculations 35
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Water Tanks Water Demand & Flow Calculations 36
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Home Assignment1. A tank is 20 x 60 by 15 deep. What is the volume in gallons?2. A tank is 60 in diameter and 22 high. How many gallons will it hold?3. A tank is 82 in diameter and 31 feet high. The flow is 1600 gpm. What is the detention time in hours?4. A tank is 120 x 50 x 14 deep. The flow is 2.8 mgd. What is the detention time in hours? Water Demand & Flow Calculations 39
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Safe Drinking Water for ALL Water Demand & Flow Calculations 40
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