Available online at www.sciencedirect.com

Procedia Environmental Sciences 10 ( 2011 ) 1926 – 1932

2011 3rd International Conference on Environmental Science and InformationConference Application Title Technology (ESIAT 2011) Wetland Restoration Suitability Evaluation at the Watershed Scale- A Case Study in Upstream of the Yongdinghe River

N.L.Ouyang a,b, S.L.Lu a*, B.F.Wu a, J.J.Zhu b, H.Wang a

aInstitute of Remote Sensing Application, Chinese Academy of Sciences, , 100101, bCentral South University, Changsha, 410083, China [email protected]

Abstract

Recently, wetland restoration has received increased attention due to multiple and valuable environmental services provided by wetlands. However, most studies have specifically focused on undertaking restoring strategies, such as improving water quality, protecting biodiversity or utilizing flood, without considering the interaction among different wetlands in a whole watershed, such as river connectivity and flow continuity. And the special effects on the restoration performance and management implications are not fully evaluated. Thus, it is needed to evaluate potential effects of wetland restoration activities in a watershed scale, in order to find suitable wetland restoration sites. This paper proposes a GIS-based multi-criteria comprehensive evaluation methodology for wetland restoration suitability evaluation, by taking upstream of the Yongdinghe River as the example. It includes three steps: criteria information extraction, criteria value assignment and normalization, and integrated evaluation. For the first step, the stream order, overland flow length, stream water quality, saturation index, hydric soil and land use were selected as the evaluation criteria. In the second step, unique value was assigned to each criterion according to their potential contribution to the restoration. And all the criteria were normalized in order to eliminate errors that may result from different dimensions. In the final step, the weight of each criterion was calculated and the integrated criterion was deduced by using the AHP method. The restoration suitability prioritization of the wetlands was classified into 5 levels: lowest, low, middle, high, highest by using the histogram segmentation method. And the evaluation accuracy was verified with the Precedence Chart Method. The statistical result shows that about 979 km2 wetlands in the overall study area has the highest suitability for restoration, accounting for 2.18% of the total area. And most of them are located in Yangyuan country, with an area of about 131.586 km2. The main types of wetlands are reservoir wetland and river wetland. They are accounting for 11.75% and 11.33% of the total area, respectively.

© 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Conference ESIAT2011 ©Organization 2011 Published Committee. by Elsevier Ltd. Selection and/or peer-review under responsibility of [name organizer]

Keywords: wetland restoration, watershed scale, GIS, multi-criteria comprehensive evaluation, AHP, Yongdinghe River.

1878-0296 © 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Conference ESIAT2011 Organization Committee. doi: 10.1016/j.proenv.2011.09.302 N.L. Ouyang et al. / Procedia Environmental Sciences 10 ( 2011 ) 1926 – 1932 1927

ĉ. Introduction

Wetland is a natural complex formed by the interaction of land and water systems, it has multiple and valuable environmental services, such as maintaining the ecological balance, protecting biodiversity, maintaining water resource, preventing flood or drought, degrading pollution and regulating climate etc[1]. It is the world's climate "stabilizer", and known as "Kidney of the Earth”. However, with the over-exploitation of wetlands by human activities , water consumption around the wetlands have increased greatly, and natural water resource as precipitation have decreased, and surface runoff supplied to wetland are cut by water conservancy or other projects, resulting in shrinkage of the wetlands, depression of biodiversity and recession of the production potential etc. If no timely measures were taken to wetland restoration, wetland structure, function and associated habitats will continued to be destroyed, thereby leading to water shortages, soil erosion, climate anomalies and other natural disasters. Therefore, it’s urgent to restore the degraded wetlands [2, 3], while the first necessary step is to analyze an accurate evaluation of its restoration suitability, so as to provide scientific strategies for sustainable use of wetlands. However, relative studies on wetland restoration have specifically focused on undertaking some restoring strategies, such as improving water quality, protecting biodiversity or utilizing flood, without consideration of the overall structure of the connectivity between wetlands, and the special effects on the restoration performance and management implications are not fully evaluated, thus it needs to evaluate potential effects of wetland restoration activities within a watershed by analyzing watershed process. Watershed is a natural complex coupling of the upper, middle and lower reaches, and select the range of a degraded wetland for restoration at the watershed scale allows for spatial arrangement of sub-watersheds in the stream network and takes into account of stream substrate types, the intersection of water and land, as well as the continuity of the process between up and downstream. Therefore, it is more scientific to evaluate wetland restoration suitability and make strategies at the watershed scale.

2. Study Area and Data

The Yongdinghe River crosses provinces of , Inner Mongolia, and cities of Beijing, Tianjin. It is west to the and the North Canal, east to the and north to the Daqing River, and the whole area of the basin is about 47016 km2. This paper selects the upstream of the Yongdinghe River as study area, where there exist two major tributaries: Sanggan River and Yang River, and the two rivers converge together as in ZhuGuantun of Huailai County in Hebei Province, with a length of 747 km. Sanggan River originated from , Shanxi Province, with a drainage area of 25840 km2, while the Yang River originated from Xinghe county in Inner Mongolia with a drainage area of 16710 km2 [4]. Yongding River is the largest tributary of the , as well as the largest river that flows through Beijing, and provides the city with a rich source of water, and has a vital importance in sand resistance and climate regulation, thus it is called the mother river of Beijing (Yin, 2003; Li, 2005). The majority topography of the basin is mountain, and the main types of wetlands include artificial canals, agricultural wetlands, urban landscape and entertainment wetlands, reservoir \ dam wetlands, stream flood wetlands and stream wetlands [5]. The main data used in the study are DEM, soil classification data [6], river water quality data [7], and vector data including villages, reservoirs, streams and land use\cover. All the vector data are obtained from the sub-project of the Key Innovation Project of Chinese Academy of Sciences, called “Environmental Effects Monitoring and Evaluation of the Hai Basin Management project Using Remote Sensing” [8].

1928 N.L. Ouyang et al. / Procedia Environmental Sciences 10 ( 2011 ) 1926 – 1932

3. Suitability Evaluation Methodology

Because factors affect the wetland restoration are numerous and complex, it is not reasonable to evaluate the restoration suitability by one indicator merely. Therefore we select numerous indicators relative to wetland restoration for the evaluation [9]. A three-step approach is proposed in the methodology: criteria information extraction, criteria value assignment and normalization, and integrated evaluation. 3.1 Criteria information extraction Considering wetland characteristics, function and the data’s availability, we selected criteria to develop the evaluation on two spatial scales: The first consists of physical parameters that define wetland properties, including hydrologic regime, soil characteristics and topography; while the second consists of parameters that characterize wetland function, including overland flow length, water quality, and stream order. Physical parameters such as hydric soil can be used as a benchmark to assess the degradation of wetlands [10]; while land use\cover influences the material and energy exchange between wetlands, thereby affecting the wetland landscape pattern [11]; and the topography determines the spatial distribution of soil moisture and wetland hydrology in the symbol of saturation index, SI. Landscape parameters as Strahler stream order and overland flow length are used to estimate site’s ability to contribute to the downstream water quality [12]. Extraction of the hydrological information depends on DEM, and the key step is to determine the flow direction of each grid by searching the steep flow for each DEM grid [13]. Calculate the total number of cells that would flow through each grid cell, recorded as the flow accumulation, and then choose a proper threshold to generate the stream, thereby getting the Strahler Stream Order and boundaries of sub- watersheds. The overland flow length is calculated by tracing the flow path downslope from each cell to the center of the next down-stream cell, while slope, calculated by computing grid elevation difference through DEM, is used to obtain the SI with flow accumulation [14]: SI ln D / tan E (1) Where Į represents the upslope drainage area, and ȕ refers to the local slope (in °). Percent difference of attainment (PDA) is used to indicate the water quality conditions [12]: (2) PDA [(length full  lengththreat )  (lengthpartial  lengthnot )]/ lengthassessed Where the subscript full, threat, partial, assessed, refer to water quality standards ĊċČ , , and č respectively. The lengths of different quality of streams are obtained from vector data of streams, reservoirs and villages of the study area [7, 8], thereby getting the PDA (in %). According to hydric soil indicators formed under the condition of saturation, flooding or ponding [15, 16], soils are reclassified into three types: hydric soil, hydric inclusions and others. Land use\covers are relished based on their suitability to the wetland restoration: kinds of urban lands, agricultural lands and woodlands are considered unsuitable for restoration, while ponds, rivers, lakes are suitable, and paddy fields, beaches and other wet areas are less suitable. Reservoirs exist are considered not to be involved in the evaluation (Table 1). 3.2 Criteria value assignment and normalization Criteria of soil and land use\cover are obtained without any calculation, and the two criteria have no value. While the value could be assigned according to their contribution to the wetland restoration with a range from 0 (not suitable) to 5 (most suitable) [17] as follows: hydric soil 5, hydric inclusion 3, and other soil types 0. And the value of land use\cover is presented in Table 1.

N.L. Ouyang et al. / Procedia Environmental Sciences 10 ( 2011 ) 1926 – 1932 1929

Table-1 Land use\cover classification as defined for analysis in the method Land use\cover value Note Roads, Urban, Industry, Railway, Village 0 Dry land, Orchard, Grassland 0 *Water area is most suitable for restoration, thus Shrub, Woodland 0 assigned value of 5. Suitability followed water are Pond, River, Lake 5* wetland, beach and paddy field, thus assigned value Paddy field, Beaches, Wetland 2ǃ3ǃ4* of 4, 3, 2 respectively. Others, Reservoir 0 Value of the stream order, hydric soil and land use\cover indicates different levels of contribution to the restoration, while the unit of overland flow length is meter, and SI just has no units and PDA equals to percentage. The criteria dimension is not uniform and it’s not comparable for the suitability analysis, thus the value should be normalized to range from 0 to 1, thereby slashing errors from different criteria dimension. Value 0 indicates the lowest suitability, while 1 means the highest level. 3.3 Integrated Evaluation In the multi-criteria comprehensive evaluation, distribution of weights to the criteria is the key step. There are numerous methods to determine weights, and all of which can be divided into two categories: one is subjective method, determining weights by comprehensive consultation, such as Fuzzy Comprehensive Evaluation Method, AHP, Efficiency Coefficient Method, etc.; the other is objective method that determines weights according to the interrelationship between indicators or the indicators variation level, such as Principal Component Analysis, Factor Analysis, TOPSIS and so on [18]. Although objective methods may avoid some subjective factors, the results cannot reflect the real importance of indicators, thus we selected Analytic Hierarchy Process (AHP) to determine weights. Information required of AHP is simple, intuitive, and this method divides a complicated problem into several levels for a gradually decomposition analysis, and handles judgments from experts in the form of numbers, considering the importance of criteria one by one to reduce the subjectivity of empowerment greatly, therefore the result is more accurate and reasonable[19]. We made questionnaires of relative importance and invited experts of hydrology, ecology and management to fill the questionnaires. Then summarized statistics into a priority matrix, calculated the igenvalue of the matrix and judged the consistent. The weights to the criteria are equal to normalization value of the igenvalue (Table 2). Table-2 Relative Importance to the Criteria stream flow hydric land criteria PDA SI weights order length soil use stream order 1 1\3 1\3 1\5 1\5 1\7 0.04 flow length 3 1 1\3 1\3 1\3 1\5 0.06 PDA 3 3 1 1\3 1\5 1\5 0.1 SI 5 3 3 1 1\3 1\3 0.15 hydric soil 5 3 5 3 1 1\3 0.25 land use 7 5 5 3 3 1 0.4

4. Result and Discussion

1930 N.L. Ouyang et al. / Procedia Environmental Sciences 10 ( 2011 ) 1926 – 1932

Results could be different with different methods or different relative importance in AHP. However, accuracy can be improved by assorting the result into levels according to the result’s normal distribution, and the greater the gap between different levels of breakpoints, the better accuracy of the result will be [20]. Therefore, five levels are chosen to indicate the wetland restoration suitability of the study area: lowest, low, middle, high, and highest, as shown in Fig.1.

Fig.1 Suitability of wetland restoration in upstream of the Yongdinghe River

Weights analyzed by Precedence Chart Method (Table 3) are used to verify the results calculated before. This method can fully express the relationship between the importance of the criteria through comparing and the result is reliable [21]. The consistency of the two results of high and highest suitability was calculated to be 0.973, which showed a good accuracy of the evaluation analyzed. Table-3 Weights of the Precedence Chart Method stream flow hydric criteria PDA SI land use sum weights order length soil stream order — 0* 0 0 0 0 0 0 flow length 1* — 0 0 0 0 1 0.067 PDA 1 1 — 1 0 0 3 0.13 SI 1 1 0 — 0 0 2 0.2 hydric soil 1 1 1 1 — 0 4 0.27 land use 1 1 1 1 1 — 5 0.333 *Value 1 indicates more important in the relative comparison between two indicators, 0means oppositely. Statistic of different suitabilities of wetland restoration in Figure 2 shows that only a little part of wetland in the Yongdinghe River has a high suitability to be restored, accounting for 2.32%, while the lowest suitability of wetland restoration takes up the most area with a percent of 52.6. And the suitability levels of low, middle and high account for 24.96%, 10.35% and 9.76% respectively. Statistic of highest suitability of wetland restoration in Figure 2 shows that Yangyuan country has the largest area of wetlands that can be restored, with an amount of 131.586 km2, and the Huailai country just follows behind, with an area of 129.086 km2. Wei country takes up the third place with an area of 103.753

N.L. Ouyang et al. / Procedia Environmental Sciences 10 ( 2011 ) 1926 – 1932 1931 km2. The other countries with areas of highest suitability for wetland restoration between 50 km2 and 100 km2 are , Huaian and Huairen, and the areas are 73.04 km2, 55.44 km2 and 52.57 km2 respectively. Statistic of the whole area of highest suitability of wetlands shows an amount of 979 km2 . Compared with Wetlands contribution of the Hai Basin in 2007, it shows that only 0.1% of the wetlands is artificial canal wetland, and urban scenery wetland takes 0.1% too. Reservoir\dam wetland accounts for 11.75%, and followed it is the kind of stream wetland with a percentage of 11.33, afterwards is agricultural wetland, 4.6%, and stream flooding wetland, 5.7%. The remaining 66.4% of the area are mostly around reservoirs and streams. For example, at downstream of the Zhenziliang Reservoir in Ying country has an area of about 21.85 km2, and along the downstream of Yang River to there exits about 87.2 km2, and along the upstream of Sangan River to the downstream of Cetian Reservoir in Datong country has an area over 90 km2. The key to restore a degraded wetland in the arid and semi-arid area is to supply enough water .Thus further research should focus on analyzing the feasibility of restoration from the point of water resources. Firstly, estimate the water storage and the minimum ecological water requirement of one wetland, and then make a comparison between the two quatities. If the water is in surplus, the recovery range could be expanded and the spare water may be supplied to wetlands in the downstream. To the contrary, if the water is in short, the recovery range must be reduced, and effective measures should be adopted to meet the need, such as transferring water from nearby, or cutting down the water that is used in recreation. Furthermore, to maintain the sustainable development of welands, actions as reducing water discharge and improving self-purification capacity of the existed wetlands are as improtant as restoring the wetlands.

Acknowledgements:

We would like to acknowledge the financial support of the Key Innovation Project of the Chinese Academy of Sciences (KZCX1-YW-08-03). Thanks to the Haihe River Water Resources Committee of China for providing the water quality data.

1932 N.L. Ouyang et al. / Procedia Environmental Sciences 10 ( 2011 ) 1926 – 1932

References

[1] K.G.Kim, H.Lee and D.H.Lee: Wetland Restoration to Enhance Biodiversity in Urban Areas-A Comparative Analysis. Landscape Ecol Eng. 7: 27-32 (2011) [2] J.S.White, S.E.Bayley: Restoration of a Canadian Prairie wetland and with agricultural and municipal wastewater. Environmental Management.25-37 (1999) [3] A.M.Melesse,V.Nangia and X.X.Wang: Wetland Restoration Response Analysis Using MODIS and Groundwater Data. SENSORS.7: 1916-1933(2007) [4] X.Y.Gong: Problems in Yongdinghe River and Suggestions. Beijing Water Conservancy.12-13 (2005) (in Chinese) [5] S.L.Lu, B.F.Wu and F.P.Li: Wetland Pattern Change in Hai Basin. Journal of Remote Sensing.15 (2):153-177 (2011) [6] Information on http:\\www1.csdb.cn [7] Haihe River Resources Commission in Ministry of Water Resources. Hai Basin Comprehensive Plan (Schedule) (2004) [8] B.F.Wu, S.L.Lu: Watershed Remote Sensing- Methodology and a Paradigm in Hai Basin. Journal of Remote Sensing.15 (2):201-211 (2011) [9] F.A.Lootsma, T.C.A.Mensch and F.A.Vos: Multi-Criteria Analysis and Budget Relocation in Long-term Research Planning. Europe Journal of Operational Research.392-305 (1990) [10] K.K.Moorhead: Evaluation Wetland Losses with Hydric soils. Wetlands Ecology and Management.123-129 (1991) [11] H.Y.Liu, Z.F.Li: Effects of Land Use\Cover Change on Wetland Landscape of Honghe Nature Reserve. ACTA GEOGRAPHICA SINICA.1515-1222 (2007) [12] D.White, S.Fennessy: Modeling the Suitability of Wetland Restoration Potential at the Watershed scale. Ecological Engineering.359-377 (2005) [13] S.K.Jensen, J.O.Domingue: Extracting Topographic Structure from Digital Elevation Data for Geographic Information Systems Analysis. Photogramm. Eng. Remote Sens. 1593–1600 (1988) [14]K.J.Beven, M.J.Kirkby: A Physically Based, Variable Contributing Area Model of Basin Hydrology. Hydrol. Sci. Bull. 43–69 (1979) [15] R.B.Atkingson, W.L.Daniels: Hydric Soil Development in Depressional Wetlands- A Cass Study from Surface Mined Landscapes. Ecological of Wetlands and Associated System.182-197 (1998) [16] D.A.Grimley, M.J.Vepraskas: Magnetic Susceptibility for Use in Delineating Hydric Soils. Soil Sci.Soc.Am. 2174-2181 (2000) [17] L.Palmeri, M.Trepel: A GIS-based Score System for Sitting and Sizing of Created or Restored Wetlands- Two Case Studies.Water Resour. Manage. 307–328 (2002) [18] N.F.Tahar, Z.Ismail, N.Z.Zamani: Students’ Attitude Toward Mathematics: The Use of Factor Analysis in Determining the Criteria. Procedia Social and Behavioral Sciences.476-481 (2010) [19] S.Sharma, D.Dubey: Multiple sourcing decisions using integrated AHP and knapsack model: a case on carton sourcing. Int J Adv Manuf Technol. 1171-1178 (2010) [20] D.V.Wandler, J.Hanning: Fiducial inference on the largest mean of a multivariate normal distribution. Journal of Multivariate Analysis.87-104 (2011) [21] L.Guo, B.Z.He and Y.G.Liu: The Application of Precedence chart in the Construction Project Risk Analysis. International Conference of Management Engineering and Information Technology.17-18 (2009)