water balance & management

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  • 1. 1 Water Balance & Management Strategy by Waqar Ahmed5 November 2009 Water Balance and Water Management Strategy Waqar Ahmed WPBG-Sharjah

2. 5 November 20092 Water Balance & Management Strategy by Waqar Ahmed Definitions Water Balance for Airport Plot Abu Dhabi Objective Computations Water Re-Use / Management Strategy Conclusion (Project Based) Water Balance & Management StrategyCONTENTS 3. 5 November 20093 Water Balance & Management Strategy by Waqar Ahmed Water Balance: In Hydrology, Water balance means equating the inflows and outflows of a system DEFINITIONS Water Balance & Management Strategy Global Water Balance 4. 5 November 20094 Water Balance & Management Strategy by Waqar Ahmed Evapotranspiration: It is sum of (water loss) through evaporation and transpiration Where transpiration is evaporation of water from Ariel parts of plants DEFINITIONS Water Balance & Management Strategy 5. 5 November 20095 Water Balance & Management Strategy by Waqar Ahmed Water Balance: I O = S/ T Where I = Inflow including the Potable water and Reliable rainfall O = Outflow including the Wastage, Evapotranspiration, Surface runoff, percolation and rain losses S = Change in storage T = Time DEFINITIONS Water Balance & Management Strategy 6. 5 November 20096 Water Balance & Management Strategy by Waqar Ahmed Water Balance for Airport Plot Abu Dhabi Water Balance & Management Strategy 7. 5 November 20097 Water Balance & Management Strategy by Waqar Ahmed Water Balance for Airport Plot Abu Dhabi Water Balance & Management Strategy 8. 5 November 20098 Water Balance & Management Strategy by Waqar Ahmed The main objectives are: To compute a complete water budget for the project clearly showing the inflows provided and outflow generated To increase the landscape area by utilizing the surplus grey water To seek the possibility of a water feature using recycled surplus water even in the low irrigation demand month (winter season) Possible reduction in water demand by use of recycled water for toilet use Review of Rain Water harvesting for use OBJECTIVE Water Balance & Management Strategy 9. 5 November 20099 Water Balance & Management Strategy by Waqar Ahmed Surface Runoff Where Pe = Excess Rainfall (mm) P = Reliable rainfall (mm) CN = Curve Number (selected depending on the land uses 58.8) S = Potential Maximum retention The twenty six years monthly rain fall data (1982-2007) has been analysed 50% reliability of the rain fall Reliability Factor = no of years x % Reliability COMPUTATIONS Water Balance & Management Strategy SP SP Pe 8.0 )2.0( 2 + = 10 1000 = CN S 10. 5 November 200910 Water Balance & Management Strategy by Waqar Ahmed Irrigation Water Requirement Where IWR = Irrigation water requirement ET0 = Evapotranspiration Kc = Crop coefficient (Grass=1 and Tree=1.3) A = Area to be irrigated ETc = ETo x Kc x A The evapotranspiration has been computed using version 4 of the CropWat software COMPUTATIONS Water Balance & Management Strategy 8.0 0 AKcET IWR = 11. 5 November 200911 Water Balance & Management Strategy by Waqar Ahmed Water Balance & Management StrategyCOMPUTATIONS 12. 5 November 200912 Water Balance & Management Strategy by Waqar Ahmed Water Balance & Management StrategyCOMPUTATIONS Item Description Inflow Outflow Remark m3 m3 Rainfall 11,558 50%reliablerainforAD Airport PotableWater 3,681,720 Averageannualdemand Wastage 920,430 25%PotableWater (Assumed) IrrigationWaterUse 1,096,077 29haoflandscapeareain project Runoff 1,223 ForCN(1)=58.8 Percolation 219,215 20%Etc RainLosses 10,333 PartofRainnotconverted intoRunoff Total 3,693,278 2,247,278 Balance 1,446,000 13. 5 November 200913 Water Balance & Management Strategy by Waqar Ahmed Water Balance & Management StrategyCOMPUTATIONS Water Balance Variation 0 20000 40000 60000 80000 100000 120000 140000 160000 180000 200000 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Months BalanceWater(m3) 14. 5 November 200914 Water Balance & Management Strategy by Waqar Ahmed Water Balance & Management StrategyCOMPUTATIONS The above water balance assumes a 100% onsite treatment of the wastewater and scenario is for full scale project development. Approximately 1.5 million cubic meters of water should be available on annual basis. Under a conventional scheme, these water will be lost in one or more of the following ways: Rejection into the drainage system Dumped into a water feature and evaporated Sold to a nearby development 15. 5 November 200915 Water Balance & Management Strategy by Waqar Ahmed MASTER PLAN Water Balance & Management Strategy 16. 5 November 200916 Water Balance & Management Strategy by Waqar Ahmed Surplus amount of water is available to irrigate an additional area of 16.5 ha By using the grey water for the toilet purposes the potable water demand can be reduced by about 23%. However the use of TSE in this way would consequently reduce the amount of land available for irrigation The current mass balance allows for a provision of a recreational lake to take up the surplus water The reliable amount of rainfall runoff per annum is 1224 m3 and therefore does not warrant a storage structure alone, however this discharge could outfall into the irrigation lake (if built) subject to the provision of oil interceptors INITIAL CONCLUSIONS Water Balance & Management Strategy 17. 5 November 200917 Water Balance & Management Strategy by Waqar Ahmed Water Balance shows that significant amount of TSE is available annually In order to maximize the useful consumption of the surplus TSE it will be required to provide storage for retaining the TSE during the low demand and high consumption months FURTHER COMPUTATIONS Water Balance & Management Strategy 18. 5 November 200918 Water Balance & Management Strategy by Waqar Ahmed Design Parameters. a. The surplus TSE is that water that is available after irrigating the landscaped areas (within project boundary) a. The onsite irrigation storage tank has been sized for storing one day onsite irrigation demand so will not be considered for retention storage. b. Recycling of a part of TSE for toilet use has not been considered in this water balance c. The evaporation (EW) from the storage pond has been estimated on the basis of pan evaporation data available for Abu Dhabi International Airport d. The irrigation water demands have been computed on monthly basis on the basis of monthly Evapotranspiration (ETO) rates computed by an industry standard software CROPWAT FURTHER COMPUTATIONS Water Balance & Management Strategy 19. 5 November 200919 Water Balance & Management Strategy by Waqar Ahmed WATER REUSE STRATEGY-OPT 1 Water Balance & Management Strategy Ponds Details Irrigation Water Use Evaporation Spill Irrigation Area No Area (ha) Vol. (m3 ) (m3) % (m3) % (m3) % Open Space in Plot (ha) Outside Plot (ha) 1 2.85 114,000 804,234 56 94,734 6.5 433,028 30 29.9 25 2 6 240,000 965,081 67 182,349 13 58,566 4 29.9 30 3 8.6 344,000 1,061,589 73 280,486 20 0 0 29.9 33 Constant pond depth of 4m 20. 5 November 200920 Water Balance & Management Strategy by Waqar Ahmed WATER REUSE STRATEGY-OPT 2 Water Balance & Management Strategy Ponds Details Irrigation Water Use Evaporation Spill Irrigation Area No Area (ha) Vol. (m3 ) (m3 ) % (m3 ) % (m3 ) % Open Space in Plot (ha) Outside Plot (ha) Many 23 344,000 257,355 26.6 710,686 73.4 0 0 18.4 8 Constant pond depth of 1.5m 21. 5 November 200921 Water Balance & Management Strategy by Waqar Ahmed CONCLUSIONS Water Balance & Management Strategy Option Pros Cons Deep Ponds (4m) More irrigation can be provided to the landscaping outside the plot (33ha max) Does not provide water feature aesthetics and vision. Shallow Ponds (1.5m) Provides water feature aesthetics and vision. Increase in evaporation reduces water available for irrigation of the landscaping out of plot to 8ha. 22. 5 November 200922 Water Balance & Management Strategy by Waqar Ahmed QUESTIONS Water Balance & Management Strategy