REVIEW

Song CHENG, Hongtao SONG

Conservation buffer systems for water quality security inSouth to North Water Transfer Project in China: an approachreview

© Higher Education Press and Springer-Verlag 2009

Abstract Water shortage is a crucial problem in northernChina, but in southern China, enormous floods frequentlyoccur. The water problems seriously disturb human life andthe sustainable development of the economy and society inthe country. To solve the water problem, the government ofChina approved the South to North Water Transfer Projectin 2002. The project will build the east, middle and westroutes in which 44.8 billion m3 of water will be transportedfrom the Yangtze River in the southern part to the northernregion annually. The east and middle routes are 1154 and1267 km long, and their respective constructions have beenstarted since 2002 and 2003. The west route is reevaluated.However, the establishment of conservation buffer systemsbeside the routes to protect the water from severe non-pointpollution from agricultural runoff was ignored. Except forpollution, change in the environment from the waterexporting to importing area also alters the physical andchemical properties of the transferred water. The protectionof the water quality along the routes is a critical issue thatsignificantly influences the purpose of the project. Thepaper proposes the establishment of conservation buffersystems beside the routes for the protection of the water,and discusses the buffer construction based on somesuccessful cases in western countries.

Keywords conservation buffer system, South to NorthWater Transfer, wetland, water quality

1 Introduction

China is subjected to serious water problems, such as watershortage, water pollution, and flood disasters.

Water shortage is severe. Although China has vast watersystems of rivers, lakes and wetlands with 2.8�1012 m3 offreshwater (ranked 6th in the world), its water volume percapita, however, is only 2300 m3 which is much lower thanthe global average of 10000 m3 (Varis and Vakkilainen;2001; Warren, 2001).Water distribution is highly heterogeneous between the

southern and northern China. In the south, precipitationranges from 1000 to more than 2000 mm yearly, and the6300 km long Yangtze River is located in the area. Theriver annually discharges 9.56�1011 m3 of water into theEast China Sea. Flood disasters often occur in the river. In1998, more than 1500 people died in floods. In 2002,flooding impacted the lives of 190 million people,damaged more than one million houses, and destroyedalmost 33 million acres of cropland. In the north, theprecipitation is between 800 and less than 250 mm, andonly 6.7% of China’s total water runoff is obtained.Although the Yellow River, which has a length of5464 km, is located in the northern China, its downstreamdries out from 10 to more than 100 days every year sincethe 1970s (Lehmkuhl and Liu, 1997). More than 150 citieshave a severe lack of water supply, including Beijing. Thewater volume per capita is 580 m3, which threatens300 million people’s lives in the area.The water shortage restricts the sustainable development

of China’s society and economy. 66% of China’s croplandis in the north, but only 25% of China’s total water isavailable. The water for a hectare of cropland is only one-eighth of that in the south. As a result, China loses over 24billion US dollars yearly, including half of the loss fromindustrial output.Water diversion is a vital means to solve the water

scarcity in the north and flooding in the south. In 2002, thegovernment of China approved the ambitious South toNorth Water Transfer Project that will take approximately40 years to construct and will cost more than 58 billion USdollars. The project will annually divert 4.48�1010 m3 ofwater from the Yangtze River to the north through three

Translated from Journal of Sichuan Forestry Science and Technology,

2008, 29(4): 1–8 [译自: 四川林业科技]

Song CHENG (✉), Hongtao SONGInstitute of Mountain Hazards and Environment, Chinese Academy ofSciences, Chengdu 610041, ChinaE-mail: chengs889@gmail.com

Front. For. China 2009, 4(4): 394–401DOI 10.1007/s11461-009-0070-y

routes, and may improve the degraded ecosystems ofapproximately 151000 km2 area. The construction of theeast and middle routes (Fig. 1) started in 2002 and 2003.The west one is in the stage of reevaluation. The east routeis 1154 km long. 1.43�1010 m3 of water will be transportedthrough the route annually. The export of water will befrom Yangzhou in Jiangsu Province beside the YangtzeRiver. The water will go through Anhui, Shandong andHebei provinces to Tianjin City. The middle route is1267 km long, and originates from the DanjiangkouReservoir located between the Danjiang River, and HanRiver as a large branch of the midstream of the YangtzeRiver (Fig. 2). The dam of the Reservoir will beconstructed to 176.6 m high from 162 m in the nearfuture. The total water storage capacity will increase to2.91�1010 m3, and 1.1�1010 m3 of the water will betransported to Beijing and Tianjin cities in the norththrough Henan and Hebei provinces.Water pollution is also serious in China. 83.4% of river

systems are polluted (Hu et al., 2001). The most commonpollutants are nitrogen and phosphorus. In China’sagricultural production, a large amount of chemicalfertilizers, pesticides and herbicides is used. However,crops absorb only 35% to 40% of the chemicals. Most ofthe chemicals flow into the river systems through runoff.Many people drink the polluted water. Based on the criteriaissued by the World Health Organization, 50 mg/L ofnitrous concentration in water is the threshold of humanhealth. A higher concentration over the threshold maydamage the kidney and liver, and cause dizziness, sight

faintness and throat cancer, if people drink it for a longtime. However, the concentration is around 300 mg/L inmost river water.In the water exporting area of the middle route, 60000 t

of chemical fertilizers and 2000 t of pesticides are annuallyused in farmlands around the Danjiangkou Reservoir, sothat N and P concentrations in the water exceed the criteriaof drinkable water issued by the China EnvironmentalProtection Agency (Chen et al., 2005). For example, itstotal nitrogen is around 1.5 mg/L (Table 1) and reaches theupper limit of medium eutrophication (Hu et al., 2001).Thus, water pollution in the exporting area and beside theroutes should be highly concerned.Additionally, the cropland environments will alter

the physical properties of the transferred water, anddegrade its quality. For instance, water temperature willincrease much in the summer due to very little forestcover in the croplands. The higher temperatureincreases bacteria populations (Clinton and Vose, 2006),decreases its pH value and dissolved O2 (Parkyn et al.,2003). Sequentially, the lower pH value inhibits denitri-fication and maintains relatively high nitrogen concentra-tion in the water (Parkyn et al., 2003; Hefting et al., 2005).However, no ecotechnology is applied to secure the waterquality.The objective of this paper is to propose the establish-

ment of conservation buffer systems along the routes formitigating the agricultural pollutants, securing the waterquality and improving ecological environments at thelocations.

Fig. 1 Map of the east, middle and west routes of South to North Water Transfer (SNWT) (made by W G SANG, Z H LU and J Z ZHAO)

Song CHENG et al. Conservation buffer systems for water quality security in South to North Water Transfer Project 395

2 Materials and methods

A successful case study has not been done in China. Thispaper is a review from a large number of publishedliteratures on conservation buffer system. The effects of thesystems on the removal of nutrients and sediments fromrunoff, the optimal structure of plant community in thebuffer systems, and several models of simulating theeffective widths of riparian buffer are discussed.

3 Results and discussion

Conservation buffer systems, such as filter strips nearcroplands, riparian forest zones between uplands and rivernetwork, and wetlands, are a primary ecotechnology toremove sediment, organic materials, and inorganic chemi-cals carried in runoff (Dosskey et al., 2005; Ice et al., 2006;Merrill and Benning, 2006; Verhoeven et al., 2006).Establishment of conservation buffer systems beside theroutes and around the Danjiangkou Reservoir is importantfor the South to North Water Transfer Project. The systems

will play vital roles in 1) protecting the water from non-point pollution in runoff; 2) cleaning the transferred water;3) increasing richness of algae, fishes, amphibian, aquaticvertebrate and invertebrate, plants and birds; 4) improvingphysical properties of the water; and 5) improving localenvironments. However, many factors affect the effects ofthe buffer systems.

3.1 Vegetation buffer systems

3.1.1 Buffer types and removal of nutrients and sediments

The removal ability varies with buffer types. Grass bufferstrips are effective in removing sediments and sediment-associated pollutants (particulate P and N) from runoff, butless effective in removing soluble nutrients, such as nitrate,ammonia, and dissolved P (Parkyn, 2004). Pasture buffercan remove 55% of nitrate and phosphorus in agriculturalrunoff (Parkyn, 2004). Switchgrass buffer removes 80% oftotal N, 62% of NO3-N, 78% of total P, 58% of PO4-P, and95% of sediment in runoff (Cooper, 1990). Riparian forest

Fig. 2 Satellite photo of the Danjiangkou Reservoir from Google Earth. The Reservoir consists of Dan pool (part 1) and Han pool(part 2) with total water area of 724 km2.

Table 1 NH4-N, NO3-N, turbidity, total nitrogen (TN), total phosphorus (TN) in water of 5 rivers in the Dangjiangkou Reservoir area (data from

Shiyue Li).

location NH4-N/(mg$L–1) NO3-N/(mg$L–1) turbidity TN/(mg$L–1) TP/(mg$L–1)

river 1 0.13 1.35 0.68 1.48 0.0050

river 2 0.14 1.40 0.76 1.54 0.0024

river 3 0.12 1.38 1.54 1.50 0.0041

river 4 0.12 1.24 7.52 1.36 0.0073

river 5 0.15 1.52 9.26 1.67 0.0134

396 Front. For. China 2009, 4(4): 394–401

buffers promote infiltration, immobilization, and transfor-mation of dissolved pollutants in runoff (Mitsch andJörgensen, 2004; Dosskey et al., 2005; Dodds and Oakes,2006; Merrill and Benning, 2006), and can reduce 97% ofNO3-N, 74% of ammonium, 68% of total ammonium, 78%of total orthophosphate masses, and 76% of sediment insurface flows. The removals result from biologicaldenitrification, plant uptake and interception (Cooper,1990; Fennessy and Cronk, 1997; Martin et al., 1999;Puckett and Hughes, 2005; Schoonover et al., 2005). Giantcane buffer greatly declines sediment mass and N by 100%(Schoonover et al., 2005, 2006). Except for the buffers,wetland systems may provide many benefits, including fishand wildlife habitats and substantial biodiversity (Mitschand Jörgensen, 2004).Multiple plant species vegetation buffer systems have

stronger ability than that of the single plant species buffersystems (Clausen et al., 2000; Lee et al., 2003; Spruill,2004; Schoonover et al., 2005; Cobourn, 2006; Heftinget al., 2006; Ice et al., 2006; Zaimes et al., 2006). Mixedbuffer of switchgrass and woody plants removes 94% oftotal N, 85% of NO3-N, 91% of total P, 80% of PO4-P, and97% of the sediment in the runoff (Lee et al., 2003).Besides the three routes, indigenous grass, shrub and treespecies should be used for the buffer establishment. Table

2 shows that some indigenous plant species may be usedfor the buffers in different sections of the middle route.Several case studies in some western courtiers suggest

the proportions of grass, shrub and tree zone widths fromthe boundary of the buffer near the croplands to the edgenear river are 25%, 25% and 50%.

3.1.2 Buffer width and removal of nutrients and sediments

Generally, the larger the buffer width is, the stronger theremoval ability is (Table 3) (Nieminen et al., 2005; Doddsand Oakes, 2006; Schoonover et al., 2006). In the buffers,7 m width is initially effective in removing sediment andsediment-bound nutrients (Lee et al., 2003), wider sizesmay reduce them by> 70% or 50%–60% (Nieminen et al.,2005). 3 or 13 m width reduces nitrate, phosphorus andsediments by 55% or 97% (Cooper, 1990); 9 or> 60 mwidth removes total nitrogen by 61% or 100% (Fennessyand Cronk, 1997). If the width is between 20 and 30 m,nitrate is removed by almost 100% (Stephanie et al., 2003;Parkyn, 2004). However, lands for such wide buffers arenot usually available beside the routes, due to the limitationof China’s land resource. Its cropland per capita is only0.11 hm2. The effective width is an important factor for thediscussed buffer construction in the routes.

Table 2 Some indigenous woody species for planting along the middle route

sections indigenous species of woody plants

Nanyang basin to the south of Lushan and Yexian Pinus massoniana Lamb., Robinia pseucdoacacia, Diospgros Kaki, Quercus,Castanea mollissima, Zizyphus jujube, Vernicia spp. Lour.,Malus pumilaMill.,Sapium sebiferum (Linn.) Roxb, Pyrus etc.

the areas to the south in Pingdingshan City all above species and Platycladus orientalis etc.

Fangcheng, Nanyang, Dengzhou and other counties and citiesto the south in Pingdingshan City

Metasequoia glyptostoboides, P. deloides Marsh, Populus�canadensisMoench, Catalpa bungei C. A. Mey, Morus alba L., Salix spp. etc.

Pingdingshan City and the Nanyang area Salix spp., P. deloides Marsh, Populus�canadensis Moench, Fraxinuschinensis, Metasequoia glyptostoboides etc.

the Mancheng and Yixian regions along the northern section ofthe middle route, and the Anyang and Jiaozuo areas in Henan Province

Robinia pseucdoacacia, Platycladus orientalis, Pinus tabulaeformis, Ailanthusaltissima, Rhus typhina etc.

the area between the northern Pingdingshan and Zhengzhou cities inHenan Province, the area of Taihang mountain between the northernHenan and western Hebei provinces

Robinia pseucdoacacia, Platycladus orientalis, Pinus tabulaeformis, Jugiansregia L., Pistacia chinensis, Quercus, Castanea mollissima, Diospgros Kaki,Hippophae spp. etc.

the region between the northern Xingtai and Xinle, as well as theXinxiang area and Jiaozuo cities

Jugians regia L., Castanea mollissima, Diospgros Kaki, Crataegus pinnatifida,Malus pumila Mill., Pistacia chinensis, Robinia pseucdoacacia, P. deloidesMarsh, Catalpa bungei C. A. Mey, Ailanthus altissima etc.

the area between the southern Anyang and Zhengzhou cities,and along the route from Beijing to Tianjin

P. deloides Marsh, Catalpa bungei C. A. Mey, Paulownia fortunei, Fraxinuschinensis, Robinia pseucdoacacia, Malus pumila Mill., Pyrusvitis, Salix spp.etc.

the area from the northern Yuxian to Xinzheng to Beijing some grass and bamboos, Salix spp., Fraxinus chinensis, Morus alba L.,Amorpha fruticosa Linn. etc.

the area in Taihang mountain between the northern Henan andwestern Hebei provinces

Castanea mollissima, Jugians regia L., Diospgros Kaki, Malus pumila Mill.,Robinia pseucdoacacia, Ailanthus altissima, Catalpa bungei C. A. Mey, Pinustabulaeformis etc.

the area from Hebei province to Beijing to Tianjin Ailanthus altissima, Salix integra Thunb., Ulmus pumila, Robinia pseucdoa-cacia, Sophora japonica, Populus tomentosa, Fraxinus chinensis, Amorphafruticosa Linn., Zizyphus jujube etc.

Song CHENG et al. Conservation buffer systems for water quality security in South to North Water Transfer Project 397

3.1.3 Modeling for the effective width

Some concept models have been developed to determinethe effective widths for large-scale riparian buffer zones,but the quality of the models varies due to someuncertainties, such as soil types, slope, etc., which causea discrepancy in the buffer widths. For example, the USGeological Survey 30-m digital elevation model under-estimates or overestimates riparian filter strip widths(Dosskey et al., 2005). Additionally, the width of riparianbuffer is designed uniformly. The design presumes thatfield runoff is uniformly distributed and a uniform level ofpollution control is obtained along the buffers. However,field runoff is commonly not uniform because of uneventopography, uneven patterns of soil conditions and farmingpractices (Dosskey et al., 2002, 2005). As a result, theuniform widths are less effective in nutrient and soilcontrol, especially in mountainous and hilly areas. Alongthe three routes, climate, geomorphology, vegetation andland use are largely variable. The concept models mayhave a low precision in the stimulation of the effectivewidths. However, some empirical approaches are stronglyrecommended (Dosskey et al., 2005).Approach 1: Dosskey et al. (2002) have proposed an

approach for heterogeneous buffer width, and separatedifferent segments of a riparian buffer based on topography(e.g. slops in hill area). Effective buffer area ratio (definedas the ratio of buffer area to field runoff area) has a strongrelationship with sediment trapping efficiency (defined asthe percent of input load retained by the buffer) (Fig. 3).The widths in various segments are calculated using thebuffer area ratios. For example, the following equation forrelationship between effective buffer area ratio andsediment trapping efficiency is developed by the authors

based on the data of the study area (slop of 1 to 9 %) byDosskey et al. (2002).

y ¼ – 0:006þ 0:010e0:035x R2 ¼ 0:99ðp < 0:000Þ (1)

where y is the buffer area ratio (%), x is the sedimenttrapping efficiency (%), and e is the exponential. If there isa 2000 m long segment of a river branch in DanjiangkouReservoir area, the average slop is< 9% in the riversides,the field runoff area is assumed to be 10 hm2 (100000 m2)based on the DEM dataset of the Reservoir, 85% sedimentremoval is desired from the runoff. From equation (1) orthe curve in Fig. 3, the buffer area ratio is 19%. Theeffective buffer area and width are 19000 m2 (= 100000 m2

� 19%) and 9.5 m (= 19000 m2/2000 m) in the riverside.Approach 2: Mander et al. (2005) recommends the

approach of removal process equation (Eq. (2)) for urbanand agricultural plains. The effective width is determinedas follows:

CL ¼ ð1 – e – kLÞ � 100% (2)

where CL is the change in concentration (%) at distance L(m) from the buffer boundary, k is the removal ratecoefficient (m–1), k =(lnC1 – ln C2)/L, C1 is the initialconcentration at the field buffer boundary and C2 is theconcentration at the distance L from the boundary. Forinstance, from the data of the study by Ghaffarzadeh et al.(1992) (Table 3), k is 0.208 by calculation. If 85%sediment removal (CL) is desired, the effective width (L) is9.15 m using the Eq. (2). However, this approach formountainous area may cause wide variation in precision.Approach 3: Caussian model as a multivariable non-

linear regression model (Fig. 4, Eq. (3)) was developed bythe authors from the data of Parkyn (2004):

Table 3 Containment removal efficiency from references. Partial data are from review of US vegetated buffers by Castelle et al. (1994). VFS =

vegetated filter strip.

contaminant buffer width/m removal slop buffer type reference

sediment 9.1 85% 7% and 12% grass VFS Ghaffarzadeh et al., 1992

NO3-N, NH4-N, PO4-P 4.6 90% grass VFS Madison et al., 1992

NO3-N, NH4-N, PO4-P 9.1 96%–99.9% grass VFS Madison et al., 1992

sediment, N, P 9.1 84%, 79%, 73% 11%–16% grass VFS Dillaha et al., 1989

sediment, N, P 4.6 70%, 61%, 54% 11%–16% grass VFS Dillaha et al., 1989

NO3-N 10 99.9% forested buffer Xu et al., 1992

N, P 19 89%, 80% forested buffer Shisler et al., 1987

nitrate, dissolved P,particulate P, N,total suspended solids

10–1367%, 55%, 80%, 85%,

87%retired pasture Smith, 1989

total nitrogen 9,> 60 61%, 100% forested bufferFennessy and Cronk,

1997

NO3-N, PO4-3-P 10 84%, 79% woody buffer Corley et al., 1999

NO3-N 10, 20–30 70%, 100% forested buffer Parkyn, 2004

398 Front. For. China 2009, 4(4): 394–401

Z ¼ 101:400� e– 0:5

x þ 1:985

38:330

� �2

þy – 48:330

75:100

� �2� �

R2 ¼ 0:97ðp < 0:000Þ ð3Þwhere Z is the total nitrogen removal (%), x is the totalnitrogen inflow (mg/L), y is the buffer width (m). Fig. 4shows relationships among the three variables. In theDanjiangkou Reservoir area, 1.48, 1.54, 1.50, 1.36 and1.67 mg/L of total nitrogen in five rivers (Table 1) areassumed to come from runoff. If the total nitrogen isremoved by 85%, the effective widths range from 5.1 to5.3 m resulting from Eq. (3).

The widths estimated by the 1st and 2nd approaches aresimilar to many results of the studies (Table 3). However,the 3rd approach likely underestimates the widths. A

possible reason is that Eq. (3) is developed frominsufficient data. The 1st approach needs to know thefield runoff areas for individual segments using the DEMdataset and the results may have some error when the slopeis> 9%. For the 2nd approach, k is affected by manyabiotic and biotic factors. The k values for the varioussegments in the routes should be determined by fieldexperimental data. In the 3rd approach, the data of totalnitrogen inflow also needs to be obtained from the field,and the model needs to be calibrated by sufficient fieldexperiment data.

3.1.4 Buffer width and aquatic biology

Wide vegetation buffer systems have a strong capacity forriver restoration. Generally, the width for aquatic biologyconservation is two times more than the width for theremoval (Lee et al., 2003). The wider systems provide richfood chains for aquatic biology (Mitsch and Jörgensen,2004; Quinn et al., 2004), and improve the water’sphysical and chemical properties. Large canopy of forestin the buffer lowers water temperature (Parkyn et al., 2003,Meleason and Quinn, 2004; Dosskey et al., 2005),sequentially restricting dissolved O2 from being releasedfrom the water and CO2 dissolved into the water (Heftinget al., 2005; Clinton and Vose, 2006). The effectscontribute to the development of aquatic biology (Parkynet al., 2003). The wider buffers also increase birdcommunities (Shirley and Smith, 2005).

3.1.5 Wetland systems

The transferred water in the routes should flow throughwetlands that can remove 60 to 100 kg P/(hm2$year) and1000 to 3000 kg N/(hm2$year) by denitrification, nutrientand sediment deposition, and aquatic plant uptake (Cooper,1990; Woltemade, 2000; Groffman and Crawfor, 2003).The effects depend on the area of wetland systems(Verhoeven et al., 2006). Many examples from the USAand Sweden indicate a global rule that wetlands cansignificantly contribute to the improvement of waterquality at the catchment level, if they account for at least2%–7% of the catchment area (Verhoeven et al., 2006).Mitsch et al. (2001) have reported 20%–50% nitrogenremoval in Mississippi River water needs with wetlandscovering 3%–7% of the total basin. Modeling has alsoshown 40% nitrogen removal requires 5% wetland area ofthe total catchment area (Arheimer et al., 2005). However,0.6% wetland area of the Rönneä catchment area fails tobring improvement (Arheimer and Wittgren, 2002). Theproportions may be useful information for establishingartificial wetland systems for the routes. Wilma H.Schiermeier Olentangy River Wetland Research Park atThe Ohio State University in USA provides a successfulcase of establishing the wetlands (http://swamp.osu.edu).

Fig. 3 Relationship between sediment trapping efficiency (%)and buffer area ratio (%). It is developed using VFSMOD forconditions on Burr farm (slop of 1 to 9%) in the southeasternNebraska, USA (data from Dosskey et al., 2002).

Fig. 4 Gaussian model for the relationship of total nitrogenremoval with riparian forest buffer width and total nitrogen inflow(data from Parkyn, 2004).

Song CHENG et al. Conservation buffer systems for water quality security in South to North Water Transfer Project 399

Acknowledgements The study was partially supported by the NationalScience Foundation of China (Grant No. 30872000) and K. C. WongEducation Foundation, Hong Kong to Song Cheng. The author would like tothank Siyue Li for the data measurement of water quality in the DanjiangkouReservoir for Table 2, meanwhile, could not forget the short-term workexperience with Quanfa Zhang who provided the egregious work conditions.

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