Environmental Flow Requirements for Integrated Water Resources

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Communications in Nonlinear Science and Numerical Simulation 14 (2009) 2469–2481 www.elsevier.com/locate/cnsns

Environmental ﬂow requirements for integrated water resources allocation in the Yellow River Basin, China

Z.F. Yang a,*, T. Sun a, B.S. Cui a, B. Chen a, G.Q. Chen b

a State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China b National Laboratory for Complex Systems and Turbulence, Department of Mechanics, Peking University, Beijing 100871, China

Received 9 May 2007; received in revised form 16 October 2007; accepted 12 December 2007 Available online 29 February 2008

Abstract

Based on the classification and regionalization of the ecosystem, multiple ecological management objectives and the spatial variability of the environmental flow requirements of the Yellow River Basin were analyzed in this study. The summation rule was used to calculate water consumption requirements and the compatibility rule, i.e., ‘‘maximum” principle, was also adopted to estimate the non-consumptive use of water in the river basin. The environmental flow requirements for integrated water resources allocation were determined by identifying the natural and artificial water consumption in the Yellow River Basin. The results indicated that the annual minimum environmental flow requirements amounted to 317.62 108 m3, which represented 54.76% of the natural river flows, while for the environmental flow requirements for the integrated water resources allocation were 262.47 108 m3, which represented 45.25% of the natural river flows. The highest percentage of environmental flow requirements was 93.64% for the river ecosystem. It can be concluded that the primary concerns should be put on the downstream river water requirements to determine the environmental flows for integrated water resources allocation in a river basin. Ó 2008 Elsevier B.V. All rights reserved.

PACS: 92.40.Qk; 92.10.Sx

Keywords: Environmental ﬂow requirements; Water resources allocation; Consumptive water use; Yellow River Basin

1. Introduction

To maintain the healthy and sustainable development of a river basin, the focus of water resources allocation has been put on the water supply for human needs, with little attention to the environment [1]. Mean- while, large amount of water should be left in or released into an aquatic ecosystem for environmental protection has been occupied for human needs in recent years. For example, up to 50% of the ﬂow from the Sacramento–San Joaquin River system that empties into the San Francisco Bay is diverted out of the

* Corresponding author. Tel.: +86 10 58807951; fax: +86 10 58800397. E-mail address: [email protected] (Z.F. Yang).

1007-5704/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.cnsns.2007.12.015 2470 Z.F. Yang et al. / Communications in Nonlinear Science and Numerical Simulation 14 (2009) 2469–2481 channel before it reaches the bay [2]. The over-demand of freshwater is often more urgent in developing countries, such as China. Freshwater discharge into the Yellow River, which is the second largest river in China, has decreased 72% between the 1960s and 1990s [3]. Therefore, environmental flows have been increasingly recognized as a central issue in sustainable water resources management [4]. Environmental flow requirement (EFR) for water resources allocation requires that a certain amount of water be purposefully left in or released into an aquatic ecosystem to maintain it in a con- dition that will support its direct and indirect use values [5]. Maintenance of EFR has also become one of the highest priorities of the management of the Yellow River Basin [6]. To assess how much of the original flow regime of a river should continue to flow down it to maintain the riverine ecosystem health, a growing number of countries now recognize the need for studying EFR and incorporating EFR into water resources management [7]. Considering the differences among ecosystem structures, EFR studies have been conducted for rivers, wetlands, forest and grassland ecosystem, as well as in cities and estuaries [8–11]. Since the 1970s, there has been a progressive evolution of methodologies for assessing the EFR of riverine, wetlands and estuarine ecosystems. Different kinds of methodologies, including hydrological index, hydraulic rating, habitat simulation and holistic ones, have been widely used [12]. Hydrological methods use flow data to estimate the EFR, which are regarded as providing low confidence EFR estimates, when there is insufficient quantitative information about how different aquatic species respond to variations of hydrological indices. Instream habitat modelling methods, such as Instream Flow Incremental Methodology (IFIM), are based on the determination of habitat pref- erence curves for species [13]. Also, habitat availability is modelled for change in discharge [14]. Considering the differences in ecosystem functions, methodology for determining the EFRs will also vary for ecosystems with different objectives on environmental production [15]. Richter et al. [16] proposed an approach for setting streamflow-based river ecosystem management targets and RVA methods concerning the spatial variation of hydrological parameters and associated characteristics of timing, frequency, duration and rates of change, in sustaining aquatic ecosystems. Parameters of geomorphology, land use, soils, climate and vegetation were considered in the study of the eco-region for describing water quality patterns in a basin [17]. River zones (confined zone, armour zone, mobile zone, meander zone and anastomosing zone) and eco- logically important flows levels were identified for determining environmental water allocations in the Cond- amine–Balonne River in Australia [18]. Considering multiple ecological management objectives, spatial variability among ecosystems and influences of hydraulic works, classification and regionalization of the aquatic ecosystem are analyzed in this paper. Then, the environmental flows are determined for integrated water resources allocation in the Yellow River Basin. Finally, based on the comparison between the EFR with the water utilization in water resources allocation, suggestions for water resource management of the Yellow River Basin are presented.

2. Integrated EFRs for basin

2.1. Classiﬁcation of EFRs for basin

EFR can be divided into a range of different categories in order to maintain the health of ecosystem with different structures. Terrestrial ecosystems (e.g., forest and grassland) and wetland ecosystems (e.g., riverine habitats) have different EFRs. Considering the different functions of river flow, in terms of both quantity and quality, as well as their temporal variability, the EFRs can be classified into several main components in a river basin as shown in Table 1. The EFR for a basin can be divided into consumptive and non-consumptive water volumes, which can be allocated as needed by managers to meet diverse ecological objectives. The quantities of water needed to ensure the replacement of evapotranspiration by vegetation, soil moisture, and evaporative losses, and to ensure the maintenance of appropriate surface areas and water depths for stability of wetland habitats, are considered consumptive uses and are mainly fulfilled by the natural precipitation. Water needed to maintain the requirements of riverine habitat and to provide adequate transport of sediments and nutrients is considered as non-consumptive use, and represents the river’s flow, which are mainly influenced by the water utilization. Z.F. Yang et al. / Communications in Nonlinear Science and Numerical Simulation 14 (2009) 2469–2481 2471

Table 1 Classification system of EFRs for basin First grade Second grade Functions Terrestrial EFRs for forest and Water requirements for evapotranspiration of vegetation, soil moisture, etc. ecosystems grass lands EFRs for Urban Greenbelt Wetland EFRs for rivers Water requirements for base flow,evaporation from water surfaces, infiltration, dilution, ecosystems EFRs for lakes sediment transport, the maintenance of riverine habitat, etc. EFRs for urban wetlands EFRs for estuaries Water requirements for freshwater wetlands, balance of salinity, sediment and nutrients, etc.

2.2. Regionalization of EFRs for basin

Besides the variability of the structures, there is also spatial variability of the ecological functions among ecosystems with different ecological objectives. To identify the ecological objectives for different ecosystems in a river basin, regionalization of the river system is necessary for determining the EFRs concerning different natural factors (e.g., hydrology and climate) and anthropocentric factors (e.g., hydraulic works). There is compatibility between the non-consumptive water requirements for different regions connected by the hydrological process in basin. The index system of regionalization of river system for determining the EFRs in the river basin is shown in Table 2.

2.3. EFRs for integrated water resources allocation

Due to the different ecosystems with various structures and functions, the EFRs should be allocated as needed by managers to meet diverse ecological objectives. However, the total environmental flows are not just the sum of the EFRs with different objectives. In this paper, the summation rule is used for calculating consumptive water requirements, i.e., the requirements for each category of water use. In contrast, the compatibility rule (or termed the ‘‘maximum” principle) is used for estimating the non-consumptive requirements; i.e., the largest value among the non-consumptive categories is adopted to represent all the categories. Thus, inte- grating the different ecological objectives considered in this study leads to the following equation for the EWR of the study area:

Xn W a ¼ W i þ MAX ðW j1; W j2; ...; W jmÞð1Þ i¼1

Table 2 Index system of regionalization of river system for determining the environmental flows Level Index Functions First level River system Identify the spatial variation of water resources and maintain the integrality of river basin Second Topographical pattern Identify the influences of topography on the ecosystem at the Basin scale level Runoff depth Identify the difference of the water resources quantity at the Basin scale Drought index Identify the variation of the climate and dry-wet conditions at the Basin scale Third level Geomorphology Identify the types of riverine habitats different from the structures Characteristics of aquatic Identify the spatial and temporal variability of the objectives for ecosystem protection ecosystem Distribution of wetlands Identify the relationship between the rivers and lakes Distribution of river reaches Indicate the spatial variability of the river reaches in the source region, upstream, midstream, downstream and estuary Hydraulic works Considering the influence of dam on the riverine habitats downstream of the hydraulic works, such as reservoir 2472 Z.F. Yang et al. / Communications in Nonlinear Science and Numerical Simulation 14 (2009) 2469–2481

3 where Wa is the total EWR (m ), MAX(a, b) denotes the maximum of variables a, b; Wi is the required con- 3 sumptive water quantity for the ith category use (m ), Wj is the total non-consumptive water volumes for category j (m3), and n and m indicate the number of the objectives (categories) for consumptive and non- consumptive water volumes, respectively. Regarding water resources management, different kinds of water requirements should be fulfilled by the natural river flow, which is defined as the original flow in a stream before development or use of natural resources within the stream’s catchments. Usually, the natural river flows are calculated based on the measured river discharge at certain section and added with the water utilization above the section, such as industrial water use, irrigation, domestic water consumption and the change of the water quantity of the reservoir, which is shown as follows:

W n ¼ W m þ W a þ W i þ W s þ W r þ W d W f ð2Þ where Wn is the natural river flows above a section; Wm is the measured river discharges at the section; Wa is the water consumption for irrigation above the section; Wi is the industrial and domestic water supply above the section; Ws is the water utilization for soil and water conservation above the section; Wr is the storage of water in the reservoir above the section; Wd is the diversion of water above the section; and Wf is the water resources for floodplain. Natural water consumptions, such as water losses for evaporation and infiltration in the area above the section, fulfill the EFRs of the terrestrial ecosystems. However, the natural water consumptions are usually fulfilled by the precipitation and are seldom influenced by the anthropocentric factors. In Eq. (2), the EFRs for compensating natural water losses are not considered in the calculation of natural river flows. Then the EFRs for compensating natural water losses should not be included in the balance of the water resources allocation in a basin. As for the wetland ecosystems in a basin, EFRs are conflicting with water requirements for industrial, irrigation and domestic water supply. Maintaining certain levels of EFRs for river, lakes and estuaries should be an important issue on the integrated water resources management for river basin. River and wetland may be connected by surface water or ground water, and connected naturally or artificially in a basin. The EFRs will also be variable due to the different relationships between river and wetland for integrated water resources allocation in a basin. The wetland is naturally supplied by the river discharge when the wetland located is inside the river reaches, then the consumptive water requirements for the wetland should not be included in the water resources allocation. As for a wetland located outside a river, which is connected to each other by an artificial supply, the consumptive water requirements should be included in the water resources allocation in the calculation procedure.

3. EFRs of the Yellow River Basin

The Yellow River originates from the mountains of Western China and spans over 5000 km before reaching the Bohai Sea in Shandong Province, with the natural river flow being 580 108 m3 in the Yellow River Basin. Water utilization is steadily increasing in the Yellow River Basin since 1980s. Annual water utilization is 480.68 108 m3 for human needs in 2000, while the water consumption is 365.89 108 m3 which is approx- imately 1.5 times higher than the average results in 1950s. Water consumption for industry and agriculture has been above 70–80% of the natural flow. Based on the hydrologic data recorded by the Lijin Station which is the last station in the downstream Yellow River, river flow has been decreasing for several decades and the frequency of complete drying or ephemeral flow has been increasing since the early 1970s. In addition, the duration of the dry periods has steadily increased [3]. In the early 1990s, drying took place annually, with an average of 100 days per year without water in the lower reaches. In 1997, the river was dry for 227 days at Lijin Station and no water reached the estuary for 330 days (Fig. 1). The longest recorded river segment without flow was 428 km, from the river mouth upstream (Fig. 2). In order to identify the multiple ecological management objectives and spatial variability among ecosystems to quantify the environmental flow requirements, classification and regionalization of the river ecosystem were conducted in the Yellow River Basin. Based on the GIS spatial overlay analysis technology and the index system of regionalization shown in Table 1, the general regionalization of river system for environmental flows Z.F. Yang et al. / Communications in Nonlinear Science and Numerical Simulation 14 (2009) 2469–2481 2473

250

200

150

100

50 Days with Dry Channel (d) 0 1990 1992 1994 1996 1998 2000 Year

Fig. 1. Number of days the Yellow River Estuary was dry from 1991 to 1999.

800

600

400

200 Length of dry channel (km) 0 1990 1992 1994 1996 1998 2000 Year

Fig. 2. Length of the dry channel in the Yellow River Estuary.

could be obtained using raster image of topographical pattern, drought index, runoff depth, and drainage map. Then, the regionalization of the river system was modified based on the clustering analysis and discrim- inant analysis considering the water resources partition and characteristics of the river reaches in the Yellow River Basin. There are 10 regions and 35 sub-regions for determining the environmental flows of the Yellow River Basin (Fig. 3).

Fig. 3. Regionalization of river basin for the EFRs of the Yellow River Basin. 2474 Z.F. Yang et al. / Communications in Nonlinear Science and Numerical Simulation 14 (2009) 2469–2481

The regionalization and the relationship between water resource partitions for environmental ﬂows of river system in the Yellow River Basin are shown in Table 3.

3.1. Base ﬂows

Base ﬂows for river reaches are calculated by using the base ﬂow index [19,20],

Table 3 Regionalization of river system for environmental ﬂows of the Yellow River Basin Regions Sub-regions River reaches Station Water resource partition I South of Tibet plateau/ I1 Heyuan to Quma Maqu Area above semi humid–humid region I2 Quma to Longyangxia Tangnaihai Longyangxia I3 Daxia River to Tao River Hongqi/Taohe Taohe Basin

II East of Tibet plateau/ II1 Longyangxia to Lijiaxia Guide Area between Long and semi humid–semiarid region II2 Lijiaxia to Liujiaxia Xunhua Lan II5 Liujiaxia to Laozhou Lanzhou

II3 Huangshui Minhe/Huangshui Huangshui Basin II4 Datong River Hengtang/Datong River

III Loess hilly region and Hetao III1 Laoshou to Qingtongxia Qingtongxia Area between Lan and plain/arid–semiarid region III2 Qingshui River and Kushui Quanyanshan/ He River Qingshui River III3 Qingtongxia to Shizuishan Sanshenggong III4 Sanshenggong to Toudaoguai Toudaoguai

IV Ordos plateau/arid region IV1 Inland area – Inland area V Loess plateau/semiarid region V2 Jinghe River Zhanjiashan/Jinghe Jinghe Basin River

V3 North Louhe River Zhuangtou/North North Louhe Basin Louhe River

V4 Wuding River and Yanhe Baijiachuan/Wuding Area between He and River River Longmen V5 Kuye River and Tuwei River Wenjiachuan/Kuye River V6 Toudaoguai to Longmen Longmen/Wubao V1 Area above Baojixia in Linjiacun/Weihe River Weihe Basin Weihe River

VI Fen-Wei plain/ VI1 Baojixia to Xianyang in Xianyan/Weihe River semi humid–semiarid region Weihe River VI2 Xianyang to Tongguan in Huaxian/Weihe River Weihe River

V Loess plateau/semiarid region V7 Area above Fenhe Reservoir Fenhe Reservoir Fenhe Basin

VI Fen-Wei plain/semi humid– VI4 Downstream of Fenhe Hejin/Fenhe River semiarid region Reservoir VI3 Longmeng to Tongguan Tongguan Area between Longmen and San Z.F. Yang et al. / Communications in Nonlinear Science and Numerical Simulation 14 (2009) 2469–2481 2475

Table 3 (continued) Regions Sub-regions River reaches Station Water resource partition VII Xiao-Xiong-Tai mountain/ VII1 Tongguan to Sanmenxia Sanmenxia Longmen and San semi humid–semiarid region VII2 Sanmenxia to Xiaolangdi Xiaolangdi Area between San and Hua VII3 Xiaolangdi to Huayuankou Huayuankou

VII4 Area above Lushi in Lingkou/Yiluohe The Yiluohe Basin Yiluohe River River VII5 Downstream of Lushi in Heshiguan/ Yiluohe River Yiluohe River VII6 Qinhe River Wulongkou/ Qinhe Basin Qinhe River

VIII Alluvial plain in the downstream VIII1 Huayuankou to Gaocun Gaocun Downstream of the Yellow of the Yellow River/semi humid– VIII2 Gaocun to Lijin Lijin River Basin semiarid region VIII3 Jingdi River – VIII4 Dawen River Laiwu/Dawen River VIII5 Downstream of Lijin –

a Xn W ¼ Q ð3Þ b n i i¼1 where Wb is the river base flow requirement; Qi is the river discharge at the ith year/month; a is the base flow index, and n is the number of year. The lower level and higher level of indices are compared in this study. The lower and the higher level of the base flow indexes are determined by the minimum monthly river discharge with 90% of guarantee ratio in dry season and flood season, respectively. Spatial variation of base flow indexes are shown in Fig. 4. Lower level of the base flow index is 18.3% in the area between Maqu and Toudaoguai stations, which is the highest one in the main stream Yellow River. Lower level of the base flow index is 9.4% in the area between Toudaoguai and Longmen stations, which is the minimum results in the main stream Yellow River. The maximum higher level of the base flow index is 75.8% in the area between Toudaoguai and Longmen stations and the minimum one is 60.0% in the area above Maqu station. The EFR for low flow decreases with increasing flow variability. Coefficient of flow variability is selected to indicate the variability of river discharge, which is calculated as follows:

100.0 Lower base flow index

80.0 Higher base flow index

60.0

40.0 Base Flow Index (%) Index Base Flow 20.0

0.0 1 2 1 2 5 1 3 4 6 3 1 2 3 1 2

Fig. 4. Base flow index in the main sub-regions of the Yellow River Basin. 2476 Z.F. Yang et al. / Communications in Nonlinear Science and Numerical Simulation 14 (2009) 2469–2481 sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi P n ðK 1Þ2 C ¼ i¼1 i ð4Þ v n 1

where Cv is the coefficient of flow variability, Ki is the ith ratio of flow variability, and n is the number of years. Fig. 5 shows the relationship between the base flow index and Cv in the main stream of the Yellow River. The lower base flow index is more related to Cv than the higher level of index. Annual base flows and the base flows in flood and non-flood season can be calculated for the main sub- regions in the Yellow River by using the base flow indexes shown in Fig. 4 and the hydrological series data (from 1956 to 2000). Spatial variation of the base flows for the main sub-regions is shown in Fig. 6. Minimum base flows are lower than 40 108 m3 in the area above Xunhua Station and the section between Shizuishan and Longmen Stations. The ratio of base flows in flood season to the annual results is about 50–60%. Table 4 shows the minimum base flows for different regions. There are four areas for analyzing the variation of minimum base flows along the main stream of the Yellow River, which include the area above the Xun- hua station (I1, I2, II1, II2), from Xunhua to Shizuoshan stations (II5, III1, III3), Shizuoshan to Longmen stations (III4, V6) and downstream of Longmen station (VI3, VII1, VII2, VII3, VIII1, VIII2, VIII5). The minimum base flows are lower than 40 108 m3 for the regions above Xunhua station and regions from Shizuoshan to Longmen stations, which are relatively lower compared with other regions of the Yellow River Basin. The minimum base flows for different regions of branch river are all lower than 12.0 108 m3 because of the smaller area of watershed compared with the main stream Yellow River. The maximum base flow requirements are 12.0 108 m3 for Huaxian station in the Weihe River and the minimum results are 0.6 108 m3 for the Daicun reservoir in the Dawen river. As for the temporal variation of the base flows,

25 50

20 40

15 30

10 20 -2.5225x -2.013x y = 30.746e y = 77.948e 5 2 10 R = 0.9072 2 Lower Basic flow index (%) index Basic flow Lower Higher Basic flow index (%) index Higher Basic flow R = 0.7981 0 0 0.0 0.1 0.2 0.3 0.4 0.5 0.0 0.1 0.2 0.3 0.4 0.5 0.6 Cv Cv

Fig. 5. Relation between the base ﬂow index and Cv for the main station in the Yellow River Basin.

100 Flood Season Non-flood Season Annual 80 ) 3 m 8 60

40 Base flow (10 Base flow 20

0 121251346312312 Regions

Fig. 6. Base ﬂows for the main sub-regions in the Yellow River Basin. Z.F. Yang et al. / Communications in Nonlinear Science and Numerical Simulation 14 (2009) 2469–2481 2477

Table 4 Minimum base flows in different regions of the Yellow River Basin Region in the Station W/Ye (%) Ye/Yr (%) Region in the Station W/Ye (%) Ye/Yr (%) main stream branch river I1 Quma 60.4 14.9 I3 Hongqi/Taohe 56.4 18.7 I2 Tangnaihai 59.9 17.2 II3 Minhe/Huangshui 52.6 20.5 II1 Guide 59.2 17.6 II4 Hengtang/Datong River 61.5 15.0 II2 Xunhua 59.0 17.8 V4 Baijiachuan/Wuding River 44.8 33.4 II5 Lanzhou 58.1 20.3 V5 Wenjiachuan/Kuye River 61.4 10.3 III1 Qingtongxia 58.6 19.8 V7 Fenhe Reservoir 58.9 14.6 III3 Shizuishan 58.8 16.6 VI4 Hejin/Fenhe River 52.6 22.1 III4 Toudaoguai 59.3 8.3 V2 Zhanjiashan/Jinghe River 58.4 22.9 V6 Longmen 58.2 10.2 V3 Zhuangtou/North Louhe River 54.1 20.3 VI3 Tongguan 57.5 14.5 V1 Linjiacun/Weihe River 55.8 14.3 VII1 Sanmenxia 56.8 13.4 VI1 Xianyan/Weihe River 55.7 10.6 VII2 Xiaolangdi 56.9 13.8 VI2 Huaxian/Weihe River 56.5 14.1 VII3 Huayuankou 57.2 15.8 VII4 Lingkou/Yiluohe River 58.4 16.9 VIII1 Gaocun 57.1 14.4 VII5 Heshiguan/Yiluohe River 56.8 17.8 VIII2 Lijin 57.6 11.9 VII6 Wulongkou/Qinhe River 58.1 20.4 VIII5 Lijin 57.6 11.9 VIII4 Laiwu/Dawen River 76.2 3.9 Note: W/Ye(%) indicates the ratio of minimum base flows in flood season to the annual minimum base flows; Ye/Yr(%) indicates the ratio of the annual minimum base flows to the annual natural river discharge. the ratio of the minimum base flows in flood season to the annual base flows ranges from 50% to 60% except for the results of the Wuding river, which is 44.8%.

3.2. Water requirements for sediment transport

The sediment load of the Yellow River is extremely high. Deposition occurs in low-energy reaches where water velocity decreases suﬃciently to allow sediment drop-out. Water requirements for sediment transport are aﬀected by the sediment carrying capacity and quantity of alluvial sediment, which can be expressed by

W t ¼ Si=Ci ð5Þ 3 where Wt are the water requirements for sediment transport (m ), Si is the quantity of alluvial sediment in river 3 reaches (t), and Ci is the sediment carrying capacity (t/m ), which is related to the characteristics of sediment. Water requirements for sediment transport are calculated for the midstream and downstream of the main stream and four major tributaries, because most of the sediments are come from this area based on the series hydrological data from 1952 to 1990. It is concluded that water requirements for sediment transport are 150 108–200 108 m3 in flood season for the main stream except for the section between Toudaoguai and Longmen. The water requirements are 100 108–150 108 m3 in non-flood season for different area of the main stream. The water requirements are 27.74 108 m3 and 22.44 108 m3 for flood and non-flood season in the Weihe Basin, which are the maximum requirements in the tributary. As for other tributaries, the water requirements are 5 108 m3.

3.3. Water requirements for evaporation

EFR needed to compensate for losses through evaporation from water surfaces is calculated as [21]

W e ¼ðEm PÞA ð6Þ where We is the net water requirement for evaporation, Em and P are the average evaporation and precipitation in the water surface area, respectively, and A is the total water surface area. Annual net water consumptions for evaporation are 11.88 108 m3 from water surface of river reaches. Water consumptions in ﬂood season are 4.63 108 m3, which is equal to 38.97% of the annual water requirements (Fig. 7). Water requirements for evaporation in the areas of Lanhe, SanHua, above Longyangxia and 2478 Z.F. Yang et al. / Communications in Nonlinear Science and Numerical Simulation 14 (2009) 2469–2481

5.0

Annual water requirements

) 4.0 3

m Flood Season 8 3.0 Non-flood Season

2.0 evaporation (10 evaporation

Water requirements for Water 1.0

0.0

Taohe Qinhe Lanhe Neiliu Jinghe Weihe Helong Fenhe Sanhua Longlan Beiluohe Longsan Yiluohe Huangshui Longyangxia Downstream

Fig. 7. Environmental ﬂow for consumption in evaporation of main rivers and tributaries in the Yellow River Basin.

8.0 ) 3 m 8 6.0

4.0

2.0 Water requirements (10

0.0 123456789 Wetlands

Fig. 8. Environmental ﬂow requirements in the wetlands of the Yellow River Basin (1. Old Yellow River; 2. Mengjin; 3. Liuyuankou; 4. Wuliangsuhai; 5. Heyang-Qiachuan; 6. Jili; 7. Yuncheng; 8. Dongpinghu; 9. Yellow River Delta).

downstream of the basin are higher than those for other areas because of the diﬀerence in weather and water surface area. Fig. 8 shows the water requirements for the typical wetlands in the Yellow River Basin. The main wetlands are located in the areas of Lan-He, Long-San, San-Hua and Downstream of the Yellow River Basin.

3.4. Water requirements for inﬁltration

Water requirements for inﬁltration are calculated based on the balance of water quantity. During certain periods, the equation of water balance can be given as

W u þ W in W l ¼ W d ð7Þ where Wu and Wd are the river discharge at the station of the upstream and downstream, respectively; Win is the water resources in the study area; Wl is the water consumptions, which includes the consumptive water in the evaporation and infiltration. Based on the calculation of Wl and the water requirements for evaporation, the water requirements for infiltration can be obtained as depicted in Fig. 9. Annual water requirements for infiltration are 39.53 108 m3 in the Yellow River Basin. While the water requirements in flood season are 21.96 108 m3, which is equal to 55.55% of the annual results. Comparing the results between different regions, it is indicated that the maximum water requirements represent 33.97% of the annual results, which is for the downstream of the basin. The water requirements for infiltration are neg- ative in the area of He-Long section, San-Hua section, Yilou Basin, Fenhe Basin and Taohe Basin, which indicated that river flows are mainly recharged by ground water in the area. Z.F. Yang et al. / Communications in Nonlinear Science and Numerical Simulation 14 (2009) 2469–2481 2479

15 ) 3 Annual water requirements m 8 Flood Season 10 Non-flood Season

0 Water requirements for infiltration (10 requirements for infiltration Water -5 R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11 R12 R13 R14 R15

Fig. 9. Environmental ﬂows for consumption in inﬁltration of main rivers and tributaries in the Yellow River Basin. (R1: the area above Longyangxia; R2: the area between Long and Lan; R3: Huangshui River Basin; R4: Taohe River Basin; R5: the area between Lan and He; R6: Jinghe Basin; R7: Beiluohe Basin; R8: Weihe Basin; R9: the area between He and Longmen; R10: Fenhe Basin; R11: the area between Longmen and San; R12: Yiluohe Basin; R13: Qinhe Basin; R14: the area between San and Huayuankou; R15: Downstream of the Yellow River Basin.)

4. Results and discussion

EFRs for water resources allocation in river reaches of the Yellow River Basin are analyzed and shown in Table 5. The EFRs are 265.24 108 m3 in the downstream of the basin, which are the maximum requirements in the main stream. As for the tributary, the maximum requirements are calculated to be 11.01 108 m3 for the Weihe Basin. Considering the compatibility between the non-consumptive water requirements for diﬀerent regions connected by the hydrological process in the concerned basin, it can be concluded that the annual EFR for the Yellow River Basin is 297.41 108 m3. As mentioned before, the water requirements for compensating natural water losses should not be included in the water resources allocation. Then, the EFR can be calculated as

Table 5 EFRs for water resources allocation in the river reaches (108 m3) Sub-areas Environmental flows Natural water consumption EFRs for water resources allocation Annual Flood Non-flood Annual Flood Non-flood Annual Flood Non-flood season season season season season season Area above 46.9 14.48 32.42 7.73 1.15 6.58 39.17 13.33 25.84 Longyangxia Huangshui Basin 8.43 3.20 5.23 0.98 0.15 0.83 7.45 3.05 4.40 Taohe Basin 10.04 3.33 6.71 0.08 0.01 0.07 9.96 3.32 6.64 Long-Lan 96.52 31.17 65.36 5.44 0.81 4.64 91.08 30.36 60.72 Lan-He 53.01 27.29 25.72 12.05 7.00 5.05 40.96 20.29 20.67 He-Long 56.12 20.33 35.79 3.63 2.86 0.77 59.75 23.19 36.56 Fenhe Basin 2.78 1.38 1.19 0.28 0.22 0.06 2.50 1.16 1.13 North Louhe Basin 1.66 1.01 0.65 0.67 0.53 0.14 0.99 0.48 0.51 Jinghe Basin 3.07 2.10 0.97 0.70 0.55 0.15 2.37 1.55 0.82 Weihe Basin 11.01 5.82 5.19 1.05 0.83 0.22 9.96 4.99 4.97 Long-San 84.21 41.78 42.43 8.78 12.11 3.33 75.43 29.67 45.76 Qinhe Basin 2 0.97 1.03 0.64 0.22 0.42 1.36 0.75 0.61 Yiluohe Basin 3.02 1.40 1.62 0.52 0.43 0.09 3.54 1.83 1.71 San-Hua 79.59 31.00 48.59 2.08 2.11 0.03 81.67 33.11 48.56 Downstream 265.24 205.24 60.00 15.24 5.24 10.00 250.00 200.00 50.00 Yellow River Basin 297.41 223.42 74.00 47.41 23.42 24.00 250.00 200.00 50.00 2480 Z.F. Yang et al. / Communications in Nonlinear Science and Numerical Simulation 14 (2009) 2469–2481

Table 6 EFRs for water resources allocation in wetlands of the Yellow River Basin Wetlands Annual water consumption (108 m3) Water supply Included in water resources allocation Yellow River Delta 5.68 Natural/artificial supply Yes Old Yellow River 0.22 Natural/artificial supply Yes Mengjin 1.33 Natural supply No Liuyuankou 1.51 Natural supply No Wuliangsuhai 4.30 Artificial supply Yes Heyang-Qiachuan 2.18 Natural supply No Jili 0.14 Natural/artificial supply Yes Yuncheng 2.14 Natural/artificial supply Yes Dongpinghu 2.72 Natural/artificial supply No Total 20.21 12.47

Table 7 EFRs for water resources allocation in the Yellow River Basin (108 m3) Item River Wetland Annual water Ratio of EFRs to requirements natural river ﬂows (%) Annual EFRs 297.41 20.21 317.62 54.76 Environmental ﬂow requirements for water resources 250.00 12.47 262.47 45.25 allocation

250 108 m3 in water resources allocation for the river reaches, while the water requirements are 200 108 m3 for flood season and 50 108 m3 for non-flood season, respectively. Water requirements compensate the water losses of evaporation and infiltration for wetlands in the Yellow River Basin in order to maintain the balance of the water quantity. It is possible to provide a stable habitat from which animals can find food, shelter and (for many species) elements essential for successful nesting. The water requirements for evaporation and infiltration should be included in the water resources allocation for the wetlands which is connected with river reaches artificially. Based on the analysis of the water supply characteristics, the EFRs for wetlands in the Yellow River Basin can be determined as shown in Table 6. EFR is 12.47 108 m3 in the water resources allocation, which equals to 61.70% of the annual water requirements for wetlands in the Yellow River Basin. Annual EFRs are compared with the water requirements for water resources allocation, which are listed in Table 7. Annual EFRs are 317.62 108 m3, which is equal to 54.76% of the natural river flows in the Yellow River Basin. The ratio of EFRs for riverine ecosystem is 93.64%. Meeting the water requirements for riverine ecosystem should be the primary concerns for maintaining the environmental flows. The water requirements are 262.47 108 m3 for water resources allocation in order to maintain the ecosystem health, which is equal to 45.25% of the natural river flows in the Yellow River Basin.

5. Conclusions

The EFRs are analyzed for integrated water resources allocation in the Yellow River Basin. Based on the classification and regionalization of river system, various ecological needs and objectives were considered in the integrated analysis of EFRs considering both consumptive and non-consumptive requirements. As can be concluded, annual environmental flow requirements are 317.62 108 m3 in the Yellow River Basin, which is equal to 54.76% of the annual water resources. The highest ratio of environmental flow requirements is 93.64% for river ecosystem. Meeting the water requirements for river ecosystem should be the primary concerns for integrated water resources allocation in basin. The EFRs for compensating natural water losses should not be included in the balance of the water resources allocation in a basin. As for the Yellow River Basin, the EFR is 262.47 108 m3 in water resources Z.F. Yang et al. / Communications in Nonlinear Science and Numerical Simulation 14 (2009) 2469–2481 2481 allocation in order to maintain the ecosystem health, which is equal to 45.25% of the annual natural water resources. Downstream of a basin is the critical area for maintaining the environmental flows in a river basin. As for the last section of the river basin, the Yellow River Estuary should be the critical area for determining the environmental flows in a river basin.

Acknowledgements

This work was supported by National Science Foundation for Distinguished Young Scholars (50625926) and National Basic Research Program of China (Grant No. 2006CB403303).

References

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