1. Asst Prof in Water Resources and Addl Controller of
Examinations, J.N.T.U. H, Hyderabad,
2. Lecturer, Dept. of Civil Engineering, Govt. Polytechnic,
Warangal – 506 001
3. Professor of Civil engineering and Director Academic and
Planning, J.N.T.U. H, Hyderabad
Abstract: Roof top rainwater collection is one of the solutions for solving or reducing the problem of water availability, where there is inadequate groundwater supply and surface sources are either lacking or insignificant quality. Average annual rainfall in the campus of Jawaharlal Nehru Technological University Hyderabad is 821mm with unutilized non-committed surplus monsoon runoff. Ground water levels are being monitored since 2008 and found to be 25 to 30 m bgl deep in pre-monsoon period and 16 to 19 m bgl in post-monsoon which indicates the ample scope for artificial recharge of rainwater. Present study deals with the geomatic approach by employing GIS, GPS and Remote Sensing techniques for identifying sites for construction of roof top rainwater harvesting structures in the study area by preparing various spatial maps. To meet the deficit water requirement in the campus through artificial recharge and re-use of ground water, three recharge structures each with a capacity of 1,00,000 litres and one reuse structure with a capacity of 2,00,000 litres have been identified using Geomatics. —————————————
Received on Oct. 2012; Published : Volume 1 Issue 4/5, 2012
Identification of Suitable Locations for Rooftop Rainwater HarvestingStructures
1. Introduction U r b a n h o u s i n g c o m p l e x e s o r r e s i d e n t i a l b u i l d i n g s a n d i n s t i t u t i o n a lb u i l d i n g s h a v e l a r g e r o o f a r e a a n d a r e a m e n a b l e f o r r a i n w a t e rharvesting. This practice is in vogue at the individual house hold levelin remote hilly areas with high rainfall and in some semi-arid areas inthe plains (IS-15797:2008). The ever more increasing problems with watere x c e s s a n d i t s s h o r t a g e , i n v a r i o u s p a r t s o f t h e w o r l d , h a v e c r e a t e df a v o u r a b l e c o n d i t i o n s f o r t h e d e v e l o p m e n t o f r e s e a r c h o n r a i n w a t e rr e t r i e v a l a n d u t i l i z a t i o n . I n m a n y c o u n t r i e s , i n c l u d i n g s o m e E u r o p e a ncountries, the demand for potable water is met from the limited sourceso f u n d e r g r o u n d s o u r c e s ( M i k k e l s e n e t a l . 1 9 9 9 ) , a s w e l l a s s u r f a c ew a t e r , w h i c h i s f r e q u e n t l y p o l l u t e d a n d n e c e s s i t a t e s h i g h f i n a n c i a loutlays for its purification. A completely different situation occurs inn e i g h b o u r i n g G e r m a n y , w h e r e r a i n w a t e r - u s a g e s y s t e m s a r e c o m m o n l ya p p l i e d ( H e r r m a n n & S c h m i d a 1 9 9 9 ) a n d t h e y c o n s t i t u t e a s i g n i f i c a n tsource of water used in toilets, as well as for other household needs.T h e c h a r a c t e r i s t i c s o f t h e s y s t e m s a p p l i e d f o r s u p p l y i n g w a t e r t osanitary appliances and f or l an d ir ri ga ti on o r wa te ri ng, their designideas and the results achieved are presented in a paper by Zaizen et al.( 1 9 9 9 ) . T h e a u t h o r s s t r e s s t h e h i g h p o t e n t i a l o f m e e t i n g t h er e q u i r e m e n t s f o r r e d u c e d - q u a l i t y r a i n w a t e r b y r a i n w a t e r c o l l e c t e d ,stored and distributed in this way. An actual commercial facility of am u c h s m a l l e r r o o f a r e a , 2 2 0 0 s q . m , e q u i p p e d w i t h a r a i n w a t e r - u s a g es y s t e m , w a s s t u d i e d i n t e r m s o f i t s f u n c t i o n i n g b y C h i l t o n e t a l .(1999). Annual savings of tap water used for specific purposes reachedquite a high level of 450%, thus enabling a return of investment outlaywithin several years, for the system installed. The suitable election oft h e c o r r e c t l y s i z e d s t o r a g e t a n k i s p a r t i c u l a r l y s i g n i f i c a n t , b e c a u s eits oversizing does not lead to any significant increase in the quantityo f r a i n w a t e r u t i l i z e d , w h e r e a s i t d o e s i n c r e a s e t h e c o s t o f s y s t e mconstruction dramatically (Chilton et al. 1999; Słys´ 2006). Gould andNissen-Petersen (1999) categorized rainwater harvesting according to thetype of catchment surface used and the scale of activity. Advantages andb e n e f i t s o f r a i n w a t e r h a r v e s t i n g a r e n u m e r o u s ( K r i s h n a , 2 0 0 3 ) . M e d i a nrainfall provides for a more conservative calculation of system sizingthan average rainfall. The median value for rainfall is usually lowert h a n t h e a v e r a g e v a l u e s i n c e l a r g e r a i n f a l l e v e n t s t e n d t o d r i v e t h ea v e r a g e v a l u e h i g h e r . I n o t h e r w o r d s , t h e s u m o f m o n t h l y m e d i a n s i sl o w e r t h a n t h e a n n u a l a v e r a g e d u e t o t h e f a c t t h a t t h e a r i t h m e t i ca v e r a g e i s s k e w e d b y h i g h - i n t e n s i t y r a i n f a l l e v e n t s . F o r p l a n n i n gp u r p o s e s , m e d i a n m o n t h l y r a i n f a l l c a n b e u s e d t o e s t i m a t e w a t e r
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availability to a reasonable degree of certainty (Krishna, 2001).
T h e t o t a l w a t e r r e q u i r e m e n t t o t h e e n t i r e c a m p u s i s t o t h e t u n e o f1 6 8 7 m3/ d a y . T o m e e t t h e e n t i r e w a t e r r e q u i r e m e n t , t h e H y d e r a b a d M e t r oW a t e r S u p p l y a n d S e w e r a g e B o a r d ( H M W S & S B ) s u p p l i e s w a t e r t o t h e t u n e1 0 0 0 m3/ d a y. T h e r e m a i n i n g 6 8 7 m3/ d a y w a t e r r e q u i r e m e n t i s b e i n g m e tt h r o u g h t h e t e n b o r e w e l l s i n t h e c a m p u s . H o w e v e r , d u r i n g t h e s u m m e rperiod, the bore wells yield and HMWS&SB supply reduce considerably, andthis deficit is met by purchasing water through tanker supply. In thisc o n t e x t , i t i s p r o p o s e d t o m e e t t h e a b o v e d e f i c i t i n d e m a n d t h r o u g hartificial recharge. The specific objective of the present study is toidentify the sites and as se ss in g th e si te c on di ti on s for constructingrainwater harvesting structures using Geomatics.
2. Study area:The area selected for present study is the campus of Jawaharlal NehruT e c h n o l o g i c a l U n i v e r s i t y H y d e r a b a d , l o c a t e d i n t h e c a p i t a l c i t y o fH y d e r a b a d , A n d h r a P r a d e s h , I n d i a w h i c h l i e s b e t w e e n l a t i t u d e s1 702 9 ’ 2 3 . 5 ’ ’ t o 1 702 9 ’ 5 0 . 3 ’ ’ N o r t h a n d l o n g i t u d e s 7 802 3 ’ 2 2 . 9 ’ ’ t o78023’41.3’’East. The areal extent of the study area is 89.19Acres. Totalexisting built-up area within the campus is 53,822.24 m2. The topographyof the area is highly undulating, sloppy and well drained. The slope ofthe ground in the campu s a n d s u r r o u n d i n g a r e a s i s f r o m North West toSouth East. The area is 594 m to 576m above msl. The campus is underlainby massive and hard grey and pink granites of Archaean age. The groundw a t e r o c c u r s i n w e a t h e r e d g r a n i t e u n d e r u n c o n f i n e d c o n d i t i o n s a n d i nj o i n t f r a c t u r e s a n d f i s s u r e s i n s e m i c o n f i n e d c o n d i t i o n s b e l o w t h eweathered mantle. Generally, weathered granite is present up to a depthof 15 m followed by hard and pink granites. Occasional fractures occurdown to depth of 100 m bgl. The climate in the study area is semi aridwith an average annual rainfall of 821mm, monsoon rainfall is 591.40 mma n d n o n - m o n s o o n r a i n f a l l i s 2 3 0 . 3 0 m m . T h e m i n i m u m a n d m a x i m u mtemperatures range from 12oC in winter and 43oC respectively. Daily meanrelative humidity is 51%. The highest wind speed 136 km/hr.
3. Methodology:M e t h o d o l o g y a d o p t e d f o r t h e p r e s e n t s t u d y c o n s i s t s o f s e v e r a l
steps. For the preparation of digital elevation model (DEM), collectionof source data like latitude, longitude and elevation data of the studyarea is essential. It was done using hand held GPS. In present study,M A G E L L A N e x p l o r i s t X L h a n d h e l d G P S i s u s e d . T h e e x p l o r i s t X L u s e si n f o r m a t i o n f r o m t h e G P S s a t e l l i t e s o r b i t i n g t h e e a r t h t o p r o v i d ed e t a i l e d i n f o r m a t i o n a b o u t e x a c t l o c a t i o n . T h e b a s i c o p e r a t i o n o f
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exploristXL is to use the GPS satellites to compute present position.This is done internally in the software of exploristXL. Land use / Landcover map of present study area is prepared from Google image. Googleimage is downloaded from internet. The downloaded image is registered inGIS. In GIS, a shape file is created for digitization. Then, the landuse / land cover features have been digitized with sketch tool. Land use/ land cover features existing in the study are classified in to threecategories namely built up area, open area, vegetation. In the presentstudy, 3D-Analyst tool has been used in Arc GIS 9.3 version to prepares l o p e m a p , a s p e c t m a p , c o n t o u r m a p a n d h i l l s h a d e m a p f r o m d i g i t a lelevation model. Arc GIS 3D-Analyst is an ArcGIS extension that providesadvanced tools for three dimensional visualization, analysis and surfaceg e n e r a t i o n . T h e m a t i c m a p s s u c h a s R o a d n e t w o r k , D r a i n a g e , C o n t o u r ,Vegetation and Built up area maps were prepared using Remote sensing,G I S a n d G P S t e c h n o l o g i e s . T h e s e t h e m a t i c w e r e i n t e g r a t e d i n G I Se n v i r o n m e n t f o r t h e i d e n t i f i c a t i o n o f s u i t a b l e l o c a t i o n s a n d c a p a c i t yf o r c o n s t r u c t i n g o f r o o f t o p r a i n w a t e r h a r v e s t i n g s t r u c t u r e s i n t h estudy area.
4. Results and Discussions:Contours of present study area are generated with 2 meter contour
interval with the help of latitude, longitude and elevation values using3D_Analyst tool in GIS environment. Highest and lowest values observedin the study area are found to be 559 and 593 m. Slope Map of presents t u d y a r e a i s p r e p a r e d f r o m D E M i n G I S w i t h s e v e n c l a s s e s n a m e l yN e a r l y L e v e l S l o p i n g , V e r y G e n t l y S l o p i n g , G e n t l y S l o p i n g , M o d e r a t e l ySloping, Strongly Slopi ng , Mo de ra te ly s te ep t o St ee p Sloping and VerySteep Sloping. The land use / land cover categories of the study areahave been grouped into three classes Viz., Built-up area (0.0477 sq.km),Vegetation (0.2689 sq.k m) a nd o pe n ar ea ( 0. 05 94 s q. km ). Thematic mapssuch as slope map, DEM map, Road network, Drainage, Contour, Vegetationand Built up area maps which were prepared using Remote sensing, GIS andG P S t e c h n o l o g i e s w e r e i n t e g r a t e d a n d i d e n t i f i e d s u i t a b l e l o c a t i o n s i nG I S e n v i r o n m e n t f o r c o n s t r u c t i n g r o o f t o p r a i n w a t e r h a r v e s t i n gstructures as shown in Table.1. Vegetation cover and swale network mapi n t h e c a m p u s h a s b e e n s h o w n i n F i g u r e 1 . T h e m a p p e r t a i n i n g t oBuildings along with Roads in the campus has been shown in Figure 2.
T a b l e . 1 D e s c r i p t i o n o f s t r u c t u r e a n d L o c a t i o n o f r o o f t o p r a i n w a t e rharvesting structures Sl. Description of structure Location
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Identification of Suitable Locations for Rooftop Rainwater HarvestingStructures
No. 1 Roof top rainwater harvesting with a
capacity of two lakh liters and useNear PG Boys (Manjeera)hostel
2 Roof top rainwater collection with ac a p a c i t y o f 1 , 0 0 , 0 0 0 l i t e r s a l o n gw i t h r e c h a r g e s h a f t s a n d s u p p o r t e dwith VRCC walls (three places)
1. Near Civil Engg. Building2. Near UGC-ASC Building3. Near Girls hostel
Figure. 1 Vegetation cover andswale network in the campus
LegendHighway_roadsRoadsbuildingsBoundary
¯
0 120,000 240,000 360,000 480,00060,000M eters
Figure. 2 Buildings along withRoads in the campus
To meet the deficit water requirement in the campus through artificialrecharge and re-use of ground water, three recharge structures each witha capacity of 1,00,000 litres and one reuse structure with a capacity of2,00,000 litres have be en i de nt if ie d. T hr ee m ea su ri ng bore wells wered u g f o r a d e p t h o f 3 0 m n e a r t h e r e c h a r g e s t r u c t u r e s f o r i m p a c ta s s e s s m e n t s t u d i e s . W a t e r l e v e l s m e a s u r e d i n t h e t h r e e b o r e w e l l s o nweekly basis were found to be 86, 85, 32 ft in the month of April, 2012and the corresponding water levels have been improved to 60, 62, 11 ftrespectively in the month of August 2012. Total water recharged in thecampus through construction of roof top rainwater harvesting structuresis 14,00,000 litres.
5. Conclusions
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Identification of Suitable Locations for Rooftop Rainwater HarvestingStructures
Large roof area is found to be available in the campus to tap the rainwater for augmenting ground water resources. The campus area is locatedi n t h e c a p i t a l c i t y o f H y d e r a b a d a n d m o s t s u i t a b l e f o r d e m o n s t r a t i v ep u r p o s e a n d L e a r n e d a n d o p i n i o n b u i l d e r s o f t h e f u t u r e , p a s s t h o u g hthese portals, hence very useful to educate and bring awareness to thesociety. DEM was prepared from GPS and GIS. The elevations obtained fromD E M a r e c o m p a r e d w i t h G o o g l e e a r t h e l e v a t i o n s . F r o m D E M , m i n i m u me l e v a t i o n i s 5 5 9 m e t e r s a n d M a x i m u m e l e v a t i o n i s 6 0 3 m e t e s . M i n i m u me l e v a t i o n i n G o o g l e e a r t h i s 5 6 2 m e t e r s a n d m a x i m u m e l e v a t i o n i s 5 9 9m e t e r s . S u i t a b l e l o c a t i o n s f o r c o n s t r u c t i n g t h r e e r o o f t o p r a i n w a t e rh a r v e s t i n g s t r u c t u r e s e a c h w i t h a c a p a c i t y o f 1 , 0 0 , 0 0 0 l i t r e s a n don e r e u s e s t r u c t u r e w i t h a c a p a c i t y o f 2 , 0 0 , 0 0 0 l i t r e s h a v e b e e nidentified using Geomatics. Geomatic approach proved to be a reliable,f a s t e r , a c c u r a t e , c h e a p m e t h o d f o r t h e p u r p o s e . T h e a b o v e s t r u c t u r e shave been constructed and daily ground water levels are being monitoreda n d f o u n d t o b e 8 6 , 8 5 , 3 2 f t i n t h e m o n t h o f A p r i l , 2 0 1 2 a n d t h ec o r r e s p o n d i n g w a t e r l e v e l s h a v e b e e n i m p r o v e d t o 6 0 , 6 2 , 1 1 f trespectively in the month of August 2012. Total water recharged in thecampus through construction of roof top rainwater harvesting structuresis 14,00,000 litres upto August 2012.
Acknowledgement:We would like to express our sincere gratitude to Central Ground WaterBoard, Ministry of Water Resources, Govt. of India for sponsoring ther e s e a r c h p r o j e c t o n d e m o n s t r a t i v e r a i n w a t e r h a r v e s t i n g s t r u c t u r e s i nJ a w a h a r l a l N e h r u T e c h n o l o g i c a l U n i v e r s i t y H y d e r a b a d , K u k a t p a l l y ,Hyderabad.
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15797:2008,13 pages2. A r t i f i c i a l r e c h a r g e t o g r o u n d w a t e r – g u i d e l i n e s I n d i a n S t a n d a r d
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Tobias, G. (1999) Case Study of a Rainwater Recovery System in aCommercial Building w it h a La rg e Ro of . Ur ba n Wa ter, 1 (4), 345–354.
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5. S ł y s ´ , D . ( 2 0 0 6 ) T h e E c o n o m i c R e s u l t o f S y s t e m A p p l i c a t i o n f o rU t i l i z i n g P r e c i p i t a t i o n W a t e r s i n F a m i l y H o u s i n g C o n s t r u c t i o n .Instal, 6, 66–69.
6. Zaizen, M., Urakawa , T. , Ma ts um ot o, Y . an d Ta ka i, H. (1999) TheCollection of Rainwater from Dome Stadiums in Japan. Urban Water,1 (4), 355–359.
7. H e r r m a n n , T . a n d S c h m i d a , U . ( 1 9 9 9 ) R a i n w a t e r U t i l i s a t i o n i nG e r m a n y : E f f i c i e n c y , D i m e n s i o n i n g , H y d r a u l i c a n d E n v i r o n m e n t a lAspects. Urban Water, 1 (4), 307–316
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9. Krishna H. 2003. An overview of rainwater harvesting systems andguidelines in the United States. Proceedings of the First AmericanRainwater Harvesting Conference; 2003 Aug 21-23; Austin (TX).
10. Krishna H. 2001. Rainwater catchment systems in Texas. Proceedingso f t h e 1 0 t h I n t e r n a t i o n a l C o n f e r e n c e o n R a i n w a t e r C a t c h m e n tS y s t e m s o f t h e I n t e r n a t i o n a l R a i n w a t e r C a t c h m e n t s S y s t e m sAssociation; 2001 Sep 10- 14; Mannheim, Germany.
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