Effects of land use change and water reuse options on urban water cycle

Available online at www.sciencedirect.com二JOURNALOFENVIRONMENTALScienceDirectSCIENCESISSN 1001-0742N1.262908_JESJournal of Enviroameotal Sciences 2010, 2(6) 923 -928www.josc.ac.cnLELEEffects of land use change and water reuse options on urban water cycleJiho Lee', Gijung Pak2, Chulsang Yoo' , Sangdan Kim?, Jaeyoung Yoon2*1. School of Ciwil, Enionmental, and Architetral Enginering, RKorea University, Seoul 136 701, Korea. E mail: kjihito@korea.ac.or2. Departmnent of Environmental Engineering, Korea Universiny, Jochiwon, Chungnam 339-700, Korea3. Department of Enmiromental System Enginering, Pukyong Narional University, Busan, 608-737, KoreaReceived 25 September 2009; revised 28 December 2009; accepted 25 January 2010AbstractThe aim of this article was to study the efects of land use change and water reuse options on an urban water cycle. A water cycleanalysis was performed on the Goonja drainage basin, located in metropolitan Seoul, using the Aquacycle model. The chronologicaleffects of urbanization were first asessed for the land uses of the Goonja drainage basin from 1975 to 2005, where the ratio ofimpervious areas ranged from 43% to 84%. Progressive urbanization was identified as leading to a decrease in evaporanspiration(29%), an increase in surface runoff (41%) and a decrease in groundwater recharge (74%), indicating a serious distortion of the watercycle. From a subsequent analysis of the water reuse options, such as rainwater use and wastewater reuse, it is conciuded that wastewaterreuse seemed to have an advantage over rainwater use for providing a consistent water supply throughout the year for a country likeKorea, where the rainy season is concentrated during the summer monsoon.Key words: Aquacycle model; land use change; water reuseDOI: 10.1016/1001-074209)60199-6IntroductionDeFee, 2007; Cuo et al, 2008; Liang et al, 2008; Franczykand Chang, 2009). There have also been numerous studiesUrbanization is an important factor that distorts theevaluating improvements in water cycle utilizing waternatural water cycle, which affects both the availabili-reuse schemes (Alegre et al, 2004; Sharma et al., 2008;ty and quality of water resources (Pouraghniaei, 2002).Lekkas et al, 2008; Han et al, 2008; Zhang et al, 2009).Urbanization increases impervious surface areas, whichHowever, no attempt has been made to consider alternativeleads to a decrease in infiltration and an increase in the water resources to improve the urban water cycle in therunoff and peak discharge (Michael and Keith, 2006).context of urbanization.The development of drainage systems for stormwater andThe objective of this study was to analyze the changessewage also causes an increase in rapid surface runoff andin the urban water cycle due to changes in land use, asreduces the amount of natural storage. Reduced infiltrationwell as perform a feasibility analysis of sustainable watermay lead to reductions in groundwater recharge and theuse options, such as rainwater use and wastewater reuse,stream base flow.to examine their infuences on water cycle. To this end, theA water cycle analysis involves the quantification ofAquacycle model was applied for a water cycle analysisvarious elements of the hydrological cycle, including(Mitchell et al, 2001; Mitchell, 2005).evapotranspiration, infiltration and runoff, etc. Such ananalysis is important in identifying the aforementioned1 Materials and methodsproblems associated with urbanization. Since the impactof urbanization on the bydrological cycle is complex,1.1 Description of Aquacycle modelafecting almost all hydrological processes (Brilly et al,2006), the water cycle is analyzed using hydrologicalThe Aquacycle is a daily urban water balance model inmodels. The use of a hydrological model and a quantitativeinvestigating the use of locally generated stormwater andassessment are essential for understanding changes in thewastewater as substitutes for imported water. The modelwater cycle as a result of urbanization and for the recoveryproduces dailv. monthlv and annual estimates of waterof a comprehensive water cycle system in urban areas.demane中国煤化工yield, evaporation,There have been many studies analyzing the effects ofimportij wastewater reuse.The mdYHC N M H efeets of stomwa-the changes in land use on the water cycle and/or qualityter and wastewater uses, and has been used to analyze theof water (Filoso et al, 2004; Chen et al, 2005; Olivera andurban water cycle in Australia to determine the optimum●Corresponding author. E-mail: jyyoon@korea.ac.kr924JiboLee et al.Vol. 22capacity for rainwater and wastewater storage (Mitchellet and public open spaces from a digital map of Seoul.al, 1999; Hatt et al, 2004).The effective impervious area was estimated using theSutherland equation (Sutherland, 2000). The impervious1.2 Application of Aquacycle modelarea maximum initial loss was taken to be 6.55 mm fromThis study considered the changes in the water cycle due the survey by Kim (2004a). The maximum recharge rateto urbanization of the Goonja drainage basin (Fig. 1), awas estimated using the permeability constant of the soilssmall urban basin located in metropolitan Seoul, Korea.in the study area. The base flow recession constant andThe area of the Goonja drainage basin is 0.964 km?; the aquifer storage capacity were taken from the study by LeeChildren's Grand Park is situated in the southeast of the (1995). Table 1 presents the Aquacycle model parametersbasin. The basin drains to the Jungrang River, northwest ofused in this study.the basin.The climatic data used in this study was the daily2 Results and discussionrainfall data provided by Gwangjin District Ofice (2005).The potential evapotranspiration was estimated using the2.1 Water cycle analysis of the Goonja drainage basinPenman equation (Penman, 1948). There are 8040 house-holds in this district, with a resident population of aboutA water cycle analysis was performed for the Goonja21,230. Therefore, the average occupancy per bhouseholddrainage basin, which consists of 83% impervious areashas been calculated as 2.64. Input data for the indoorin 2005, using the Aquacycle model. Figure 2 ilustrateswatler usage profile was estimnated using the data from the annual water cyele of the Goonja drainage basin. Fromthe survey conducted by the Seoul Development Institutethe simulation of the urban water cycle, it was identified(Kim, 2004b).that, of an annual total of 1388 mm rainfall, 306 mm wereThe average area of a unit block was estimated fromlost through evapotranspiration. The annual total surfacea 1:3500 map of Seoul and the areas of the basin, roads runof was 1044 mm, of which 937 and 107 mm were fromimpervious and permeable areas, respectively. Finally, anannual total of 99 mm of rainfall was recharged into thegroundwater. In summary, of the total rainfall, 75% formedsurface runof; whereas, groundwater recharge accountedAfor only 7%. This suggests a serious distortion in the watercycle, which can be atributed to urbanization.It was also identified that annual leakages from thereticulation system accounted for 357 mm, which is greaterthan the amount of groundwater recharge. This implies thatleakages may be able to replenish the decrease in ground-water recharge caused by urbanization. Another sourcefor recharge can be from water imported for landscape3irrigation, which may also increase the stream base flow(Hirsch et al, 1990; Paul and Meyer, 2001; Greer andStow, 2003; Michael and Keith, 2006). However, there areinstances where part of these leakages flow into the sewagecollection system; therefore, not all of the leakages can beconsidered as contributing to groundwater recharge.Another problem caused by urbanization is the drying ofFig 1 Schemaic of the Goonja dnainage basin. 1-10: subcatchment3.stream, which also relates to a decline in the grouodwaterTable 1 Model parameters for the apication of the Aquacycle model.Unit block scaleCluster scaleMeasured pararnetersAverage of unit block (m2)74.83Total area (ha)96.39Area of garden (m2)4.54Road area (ha)23.87 .Area of roof (m2)45.41Area of public open space (ha)12 39Area of pavemeat (m2)24.88Leakage rate (%)11Calibrated parametecsPercentage area of storage I (%)28Road area maximum initial loss (mm)Pervious storage 1 capacity (mm)36.80Efective road area (%)96.90Pervious storage 2 capacity (mm)86.50Base fow index (ratio)0.45Roof area maximum initial loss (mm)6.55Base flow recession constant (natio)0.012Efective roof area (%)中国煤化工0.10Paved area maximum initial loss (mm)0.12Effective paved area (%)YHCNMHG152Aquifer storage and recovery parametersStorage capacity653,389Maximum aquifer recharge rate (m/day)13.83No.6Effects of land use change and water retuse options on urban water cycle925↑电Imported waiere, (1388mm)3253 mm)Evapotranspirationg(212 mm)Outdooremse(231 mm)(1157 mm)LeakagePervious surface-soil(8 mm)Impervious(357 mm)Indoormoisture storesurface(2830 mm)Runoffinfiltration Runoff， InputRecharge(1mm) (107 mm)、 (937 mm)(99 mm)”Wastewater(136 mm sewer (2967 munj一Flow pathBaseGroundwaterFStormwaterWater(456 mm)drainage (1364 mm)storeUrban rinll-stomwater runoff networkPotable supply-wastcwater disposal networkFig2 Annual water cycle of the Goonja drainage basin.level. A separate calculation, using an accounting model1975 to 2005, at five-year interval, using land use maps.of groundwater storage, was performed using the amount Figure 3 shows the change in the water cycle due toof recharge obtained from the Aquacycle model to assessurbanization over this period.the effects of groundwater use and forced pumping. ForThe water cycle analysis clearly showed that the hy-2005, for which data for the groundwater usage anddrological components, such as evapotranspiration, surfaceforced pumping at a subway station were available, the runoff and groundwater recharge, were highly dependentgroundwater storage level was estimated to decrease byon changes to impervious areas. Especially, a sharp changeabout 110 mm per year.in hydrological components occurred between 1975 andFrom our experience of the Aquacycle model, the es-1985 when Seoul experienced the greatest amount urban-timation of the recharge parameter, BI (base flow index), ization due to the increased industrialization of Korea.has been identified as being rather empirical, as it lacksFrom 1975 to 2005, the impervious areas doubled, result-physical meaning. For a more systematic detemination ofing in areduction in evapotranspiration of 29%, an increasethis parameter, the use of the well-established SCS Curvein surface runof of 41% and a decrease in groundwaterNumber method was considered for the computation of the recharge of 74%.recharge. To incorporate this method with the Aquacycle2.3 Effectiveness of rainwater use and wastewater reusemodel, groundwater recharges obtained using the Aquacy-cle model were fitted to those estimated via the SCS curveThe efects of rainwater use and wastewater reuse on thenumber method for different hydrological soil groups (A water cycle in the study area were also examined usingto D). Table 2 presents the groundwater recharge valuesthe Aquacycle model to evaluate potential improvementsfor each sCS hydrological soil group and the relevant BI ofof the water cycle. The use of reusable water was limited tothe Aquacycle model. The proposal of using the Scs curve landscape irigation and toilet water; the analysis showedoumber method was thought to provide a more systematican annual maximum reusable water demand of 890 mm.way in determining the BI value.This ranslates to an annual reduction of 1000 mm inthe imported water supply when the leakage from the2.2 Efects of urbanization on water cyclereticulation system is considered.The chronological effects of urbanization on the waterThe determination of the optimal rainwater and wastew-cycle were studied for the Goonja drainage basin fromater storage capacities is based on the volumetric reliabil-ity, which is defined as the ratio of total volume suppliedTable 2 Groundwater recbarge corresponding to diferent hydrologicalto that demanded during the simulation period (Mitcbell,soil groups2005). Optimization of the storage size is achieved bySoil groupGroundwater recharge (mm/yr)Base fow index (BDfinding the optimal volumetric reliability at which anyfurther7830.60中国煤化is iucit ”6660.51justify-age size.430011modelInCHCNMHa), the Aquacycleulorage capacity of50000 m3 was required to meet the maximum reusable926JihoLee etal.Vol. 2210000.E 4006040-E 30019701980199020002010200199Year1200400|c冒品300300 t100 t60970Flg3 Changes in the water cyele due 1o0 urbanization (间) impervious area ratio; (b) vapotaspiation; (2) surface nnof; (d) groundwater recharge.water demand. Such a requirement was identified as beingtreatment plant with a capacity of 2700 m3 was determinedpractically impossible (62 m/household) considering theas the optimal capacity, and this would meet the maximumreasonable size of a rainwater tank for installation atreusable water demand. It was shown that a water supplyeach household. The optimal capacity estimated using thesaving of 31% could be achievedI from the reuse ofAquacycle model was 25,000 m3, which translates to awastewater, with a 30% reduction in wastewater.more realistic 3.1 m3/household. It was shown that anFigure 4c ilustrates the efects of the reuse optionsannual imported water supply of 427 mm can be savedon the urban water cycle. From the analysis of the reusethrough rainwater use, which translates to a water supplyoptions, it was identified that wastewater reuse was moresaving of 13%, with a 36% reduction in surface runof.effective than rainwater use in reducing the imported waterIn the case of wastewater reuse (Fig. 4b), a wastewatersupply (more than three times) for a heavily populatedImponted w aterImported waterReduction of imported waterReduction of inn of imported waterReductonotimpornedwater! Reduction of i* Surface nunoffSurface runoffJ Surface runoff350040004500abc|3000曼300复35002500文3000包2500-g 25001500100050500中国煤化工.9~ 100 200 300 400 500 600 700。01000 2000 3000 4CNMHGank WastewaterRain tank volume (x 1000 m')Wastewater reuseMYHreuseFlg4 Determination of the optimal capaities and their efects on the water cycle. (a) rainwater, 6) wastcwater, (Q) efecets of reuse options.No.6Effects of land use change and water reuse options on urtban water cycle927district, such as the Goonja drainage basin. Korea is richBilly M, Rusjan s, Vidmar A, 2006. Monitoring the impact of ur-in rainfall, but about two-thirds of the rainfall occurredbanization on the Glinscica stream. Physics and Chemistryduring summer months. It would require a huge storageof the Earth, Pars NB/C, 31(17): 1089- -1096.volume to contain this rainwater for reuse, which wasChen L D. Peng HJ, Fu B J, Qiu J, Zhang s R, 2005. Seasonalvariation of nitrogen-concentration in the surface water andidentified as an impractical option. For a reasonable sizedits relationship with land use in a catchment of northemrain tank, as estimated above, the amount of reusable waterChina. Joumal of Environmental Sciences, 17(2): 224- -231.that can be held is limited due to the excessive surplus ofCuo L, Lettermaier D P, Mattheussen B V, Storch P, Wiley M,rainfall. In contrast, a large volume of wastewater occurs2008. Hydrologic prediction for urban watersheds with thesteadily throughout the year. Therefore, it can be saidDistributed Hydrology- Soil-Vegetation Model. Hydrologi-that wastewater reuse has an advantage over rainwater usecal Process, 22(21): 4205- 4213.in providing a consistent water supply for the climaticFiloso s, Vallino J, Hopkinson C, Rastetter E, Claessens L, 2004.conditions experienced by Korea. However, in terms ofModeling nitrogen transport in the Ipswich River Basin,flood control, rain tanks still have an edge over wastewaterMassachusetts, using a hydrological simulation program inreuse, which contribute to reducing surface runoff whenfortran (HSPF). Joumnal of the American Water Resourcesthere is no difference between the potential wastewaterassociation, 40(5): 1365-1384.Franczyk J, Chang H, 2009. The ffects of climate change andreuse options.urbanization on the runoff of the Rock basin in the Portlandmetropolitan area, Oregon, USA. Hydrological Process,3 Conclusions23(6): 805- -815.In this study, the Aquacycle model was used to estimateGreer K A, Stow D A, 2003. Vegetation type conversion in LosPenasquitos Lagoon: An examination of the role of wa-the components of the annual water cycle for the Goonjatershed urbanization. Emvironmental Management, 31(4):drainage basin in metropolitan Seoul. The results suggest489- -503.there has been a serious distortion in the water cycle,Gwangjin District Office, 2005. Gwangjin District Statsticalcharacterized by increased stormwater runoff (75% of theYearbook. Gwangjin District Ofice, National Statisticaltotal rainfall) and decreased infiltration (7% of the totalOfice, Korea.Han y, Xu s G, Xu x z, 2008. Modeling multisource multiuserrainfall), which can be attributed to urbanization.waterresources allocation. Water Resources Management,Chronological effects of urbanization were also asessed22(7): 911- -923.for land uses of the Goonja drainage basin from 1975 toHatt B, Deletic A, Fletcher T, 2004. Integrated stormwater2005, where the impervious area ratio increased from 43%treatment and reuse inventory of australian practices. Into 84%. Progressive urbanization was identifed as leadingtermational WSUD Conference 2004, Adelaide, Australia.to a decrease in evapotranspiration (29%), an increase235 -245.in surface runoff (41%) and a decrease in groundwaterHirsch R M, Walker JF, Day J C, Kllio R, 1990. The infuence ofrecharge (74%).man on hydrologic systems. In: Surface Water HydrologyThe performance of water reuse scenarios was evaluated(Wolman M G, Riggs H C, eds.). Vols. 0-1. Geologicalto assess their feasibility for improving the water cycle bySociety of America, Boulder, CO, USA.329 -359.promoting less stormwater runof and reducing the needKim H, 2004a. Monitoring and hydrologic cycle analysis ofCheonggyecheon restoration project. Korea Institute offor imported water supply. It was shown that a saving ofConstruction Technology, Goyang, Korea.13% in imported water supply could be achieved by theKim K, 2004b. A basic study on the household consumption ofuse of rainwater, with a surface runoff reduction of 36%.tap water. Seoul Development Institute, Seoul, Korea.It was also found that a water supply savings of 31%, withLee D, 1995. Application of the groundwater recession curvesa 30% reduction in wastewater, could be achieved by theto estimate groundwater recharge and to forecast long-flow.reuse of wastewater.Ph. D Dissertation. Korea University, Seoul, Korea.Wastewater reuse seems to have an advantage over theLekkas D F, Manoli E, Assimacopoulos D, 2008. Integrateduse of rainwater for providing a consistent water supplyurban water modeling using the AQUACYCLE model.throughout the year for a country like Korea, where theGlobal NEST Jourmnal, 10(3): 310 -319.rainy season is concentrated during the summer monsoon.Liang T, WangS N, CaoH Y, ZhangCS,LiHT,LiH P,2008. Estimation of ammonia nitrogen load from nonpointAcknowledgmentssources in the Xitiao River catchmeat, China. Journal ofErvironmental Sciences, 20(10): 1195-1201.This research was financially supported by a KoreaMichael D W, Keith A G, 2006. The eets of watershed urban-University Grant.ization on the stream hydrology and riparian vegetation ofLos Penasquitos Creek, California. Landscape and UrbanPlanning, 74(2): 125-138.ReferencesMitchell V G, 2005. Aquacycle User Guide. CRC for CatchmentHydrology. Monash University, Melbourme, Austalia.Alegre N, Jffrey P, McIntosh B, Thomas J s, Hardwick I, RileyMitchel中国煤化工.2001. Modelling theS, 2004. Strategic options for sustainable water manage-:deling and Software,ment at new developments: the application of a simulationMHCNMHGmodel to explore potential water savings. Water Science andMitchell. 1999 The reuseTechnology, 50(2): 9 -15.potential of urban stormwater and wastewater. Industry928JihoLee etal.Vol. 22Report 99/14. CRC for Catchment Hydrology, MonashManagement, Natural Resources Research Center ofUniversity, Melbourne, Australia.Semnan, Semnan Province, IranOlivera F, DeFee B B, 2007. Urbanization and its ffect on runoffSharma A K, Gray s, Diaper C, Liston P, Howe C, 2008.in the Whiteoak Bayou watershed, Texas. Joumal of theAssessing integrated water management options for urbanAmerican Water Resources Association, 43(1): 170-182.developments - Canberra case study. Urban Water Joumnal,Paul M J, Meyer J L, 2001. Streams in the urban landscape.5(2): 147-159.Annual Review of Ecology and Systematics, 32: 333 365Sutherland R C, 2000. Methods for estimating the eectivePenman H L, 1948. Natural evaporation from open water, bareimpervious area of urban watersheds. The Practice ofsoil, and grass. In: Proceedings of the Royal Society ofWatershed Protection, Article 32, 193-195.London. Series A: Mathematical and Physical Sciences,Zhang Y, Andrew G, Ashok s, Chen D, Chen L, 2009. Assess-193: 120-146.ment of rainwater use and grey water reuse in high-risePouraghniaci M J, 2002. Effects of urbanization on quality andbuildings in a brown field site. Water Science and Technol-quantity of water in the watershed. MSc of Watershedogy, 60(3): 575- -581.中国煤化工MYHCNMHG