Environmental Water Requirements Research Articles

Assessment of Land Use Impact on Water-Related Ecosystem Services Capturing the Integrated Terrestrial−Aquatic System

Although the importance of green (evaporative) water flows in delivering ecosystem services has been recognized, most operational impact assessment methods still focus only on blue water flows. In this paper, we present a new model to evaluate the effect of land use occupation and transformation on water quantity. Conceptually based on the supply of ecosystem services by terrestrial and aquatic ecosystems, the model is developed for, but not limited to, land use impact assessment in life cycle assessment (LCA) and requires a minimum amount of input data. Impact is minimal when evapotranspiration is equal to that of the potential natural vegetation, and maximal when evapotranspiration is zero or when it exceeds a threshold value derived from the concept of environmental water requirement. Three refinements to the model, requiring more input data, are proposed. The first refinement considers a minimal impact over a certain range based on the boundary evapotranspiration of the potential natural vegetation. In the second refinement the effects of evaporation and transpiration are accounted for separately, and in the third refinement a more correct estimate of evaporation from a fully sealed surface is incorporated. The simplicity and user friendliness of the proposed impact assessment method are illustrated with two examples.

Using an economic framework to inform management of environmental entitlements

AbstractThere is much in the scientific literature dealing with methods to determine environmental water requirements in streams. However, most of these methods are suited to long‐term water resource planning and setting regulatory targets. In Australia, the environment is now recognized as a legitimate user of water with its own water entitlement. With this in mind, and in the context of a water market, transparent decisions need to be made as to how best to utilize environmental water reserves on yearly, monthly or even daily basis. Environmental water managers must identify priority flow components and environmental assets. This will call for information on environmental water requirements to be presented in a manner that informs operational decisions. This paper proposes that describing environmental requirements as a function relating to different flow levels, a relationship named here as an environmental response curve, is an important first step in making transparent decisions to achieve the best outcome from limited environmental entitlements. The environmental response curves allow the marginal benefit of water (or value of each additional ML) to the environment to be understood. This allows environmental recommendations to be more readily translated into operational rules. This is not a new environmental flows methodology. The contribution of this paper is representing existing data to allow operational decisions. This paper provides a possible way forward in representing environmental demands for operation of environmental water and highlights areas where our current knowledge falls short. Copyright © 2009 John Wiley & Sons, Ltd.

Ecological and environmental water requirement in the middle Yellow River

As a significant factor for maintaining river ecosystem function, ecological and environmental water requirement of riv- ers is a key issue of hydrological research. Based on real conditions of the middle Yellow River, a few methods (Montana method, minimum monthly mean discharge method, etc.) were adopted to calculate ecological and environmental water requirement of the river. The results show that in the middle Yellow River the environment water requirement is 47.356×108 m3, the water requirement for sediment delivery is 40.666×108 m3, and the water surface evaporation is 10.314×108 m3. Total tributary ecological and envi- ronmental water requirement from Kuye River, Wuding River, Fen River, Jing River, Beiluo River, Wei River, Yiluo River, and Qin River is respectively 2.071×108 m3, 3.393×108 m3, 10.143×108 m3, 8.699×108 m3, 3.575×108 m3, 34.601×108 m3, 6.481×108 m3 and 2.505×108 m3. Due to the non-independence of the middle Yellow River, further ecological and environmental water requirement research is recommended.

Modeling water supply and demand scenarios: the Godavari–Krishna inter-basin transfer, India

The Government of India's National River-Linking Plan (NRLP) aims to alleviate emerging water scarcity problems by transferring water from well endowed to more deficient areas. This study evaluated the plausible future scenarios of water availability and use under conditions of various cropping patterns, and with the explicit inclusion (for the first time) of environmental water requirements for one of the links of the NRLP: from the Godavari River at Polavaram to the Krishna River at Vijayawada—the ‘Polavaram Project’. The scenarios were evaluated using the WEAP (Water Evaluation and Planning) model. The study generates information for use in managing emerging trade-offs. The importance of explicit accounting for monthly variability in description of water supply and demand, in the monsoon-driven climate conditions of the region, is advocated. Such detailed scenario simulations and inclusion of previously unaccounted for factors/uses can help to create awareness of potential future problems, inform water management practices and suggest management alternatives. Results show that the proposed water storage and transfer will reduce water deficit within the project command area and significantly reduce dry slow river flow into the Lower Godavari Delta.

Simulating the hydrology and total dissolved solids (TDS) of an ephemeral river in South Africa for environmental water requirement determinations

AbstractExisting hydrological approaches to support the determination of environmental water requirements (EWRs) were largely developed for perennial rivers and may not be applicable to ephemeral rivers, where the quantity and quality dynamics of pool storage and frequency of connection can be more important than flow rates. The current understanding of semi‐arid hydrological processes and how best to apply hydrological models in ephemeral systems is less well developed than for more humid regions. The paper reports on the application of monthly and daily time‐step rainfall‐runoff models to simulating the hydrology (including pool storage) of the Seekoei River basin, a tributary of the Orange River in the Northern Province, South Africa. The hydrological response of the basin is spatially variable, a relatively small part of the basin generating a large proportion of the total stream flow. The outputs from the hydrological models have been used as inputs to a simple water quality mass balance model designed to simulate the total dissolved solids (TDS) of both flow and pool storage. The results from both the water quantity and quality models are encouraging when compared with the available observed data. While there are no data to confirm the simulation results at sub‐basin scales, they do appear to be conceptually acceptable. The conclusion is that the results are adequate to support ecological studies in the determination of EWRs. Copyright © 2008 John Wiley & Sons, Ltd.

A simulation framework for water allocation to meet the environmental requirements of urban rivers: model development and a case study for the Liming River in Daqing City, China

In this paper, we describe the development of a simulation framework for allocating water from different sources to meet the environmental flows of an urban river. The model permits the development of a rational balance in the utilization of storm water, reclaimed water from wastewater treatment plants, and freshwater from reservoirs with consideration of the limited capacities of different water resources. It is designed to permit the full utilization of unconventional water sources for the restoration of river water quality by increasing river flow and improving water quality. To demonstrate practical use of the model, a case study is presented in which the model was used to simulate the environmental water allocation for the Liming River in Daqing City, China, based on the three water sources mentioned above. The results demonstrate that the model provides an effective approach for helping managers allocate water to satisfy the river’s environmental water requirements.

Response of reed community to the environment gradient-water depth in the Yellow River Delta, China

We investigated and monitored a reed community in the fields. Data on the bio-ecological characteristics and β-diversity of reed communities in different environmental gradients (mainly based on water depth) of the Yellow River Delta were collected through multianalysis, extremum analysis and β-diversity index analysis. In accordance with the square sum of deviations (Ward) cluster analysis, 10 sampling plots were divided into six types with the dominant plants in different plots varying according to the change in environmental gradients. The dominant plants in these plots varied from aquatic plants to xerophytes and salt tolerant plants as water depth decreased. The average height and diameter of the reeds at breast level were significantly correlated with the average water depth. The fitness curves of average density and coverage with average water depth were nonlinear. When the average water depth was 0.3 m, the average density and coverage of reeds reached the apex value, while the height and diameter of the reeds at breast level increased with the water depth. There were obvious changes to the environmental gradient in the Yellow River Delta. The transitional communities were also found to exist in the Yellow River Delta by β-diversity analysis. Vicarious species appeared with the change in water depth. The occurrence of substitute species is determined by the function of common species between adjacent belts. The different functions of common species led to differences in community structure and function and differences in dominant plants. The result reflects the variations of species present in different habitats and directly reflects environmental heterogeneity. The values of β-diversity indices of adjacent plots were higher than those of nonadjacent plots. There are transition zones between the xerophytes and aquatic plants in the Yellow River Delta. In an aquatic environment, the similarity of reed community is higher than that of xeromorphic plants. The β-diversity index can reflect plant succession trends caused by the change in environmental gradients in the Yellow River Delta. The β-diversity index reveals plant responses to changes in environmental gradient and is helpful in observing changes in patterns of species diversity in relation to environmental gradient change and evolving trends in the future, which in turn plays a prominent role when environmental water requirements of wetland are discussed.

Substitution between water and other agricultural inputs: Implications for water conservation in a River Basin context

Substitution of irrigation water with other agricultural inputs could be an important means to conserve water in the face of growing pressures on water resources from both nonagricultural water demands and environmental water requirements. This paper discusses the potential of such substitution through an empirical analysis based on a multiple-input crop production function at the field and farm scales complemented with a numerical modeling exercise at the basin scale. Results from the crop production function analysis show that under both crop yield and net profit maximization, water is a substitute to other crop inputs for high-value crops, and is a complement to water for low-valued crops. At the basin scale, an integrated economic–hydrologic river basin model is used to analyze the role of other factors in crop input substitution, including the spatial connections among water sources and demands, hydro-agronomic conditions, and institutional settings for water allocation. Results show that in the case study area, the Maipo River basin in Chile, where water is very scarce, moving from the current, input-constrained, situation to full optimization of water resources leads to an increase in all crop inputs, including water. In that case, 301 million m 3 of additional water use results in additional net profits of USD 11 million. However, if the water fee is raised by a factor of eight while overall basin irrigation profits are maintained at the original, baseline level, a reduction of water withdrawals by 326 million m 3 is traded off with costs of USD 43.2 million for other inputs. Irrigation districts with a high share of low-value crops have a low potential for substituting water with other crop inputs. Therefore, investments for water substitution should also be kept low in these areas.

Environmental water requirements and sustainable water resource management in the Haihe River Basin of North China

Lack of consideration of environmental water requirements (EWR) in water resource allocation has caused several environmental problems in the Haihe River Basin, North China. This highlights an urgent need to study EWR and ensure instruments for sustainable water resource management in the basin. In this study, EWR scenarios were calculated for 2010 and 2030, giving values are 6.58 billion m3 in 2002, 9.22 billion m3 in 2010, and 11.62 billion m3 in 2030. Three policies and management instruments were used to address EWR, including the South–North water transfer scheme, water price policy modifications and agricultural water saving. Compared with lack of adoption of such measures, these three management instruments may mitigate acute water scarcity and lead to some improvements. This paper attempts to establish a link between adoption of measures, impact on water user sectors and environmental consequences. It also provides a basis for discussion about the effectiveness of these measures and notes additional controversies among technical, political and economic instruments.

Determination of environmental water requirements of Lake Urmia, Iran: an ecological approach

Lake Urmia is a thalassohaline ecosystem. It is an extremely simple ecological pyramid. This makes it a very sensitive ecosystem. This ecosystem has been facing various threats regarding the amount of water released from the associated basin. To calculate the lake water requirement with an ecological approach, we identified three variables: ecology, water quality, and water quantity indices as environmental indicators. The ecological index represented by Artemia urmiana is considered as an independent variable; while, the water quality index represented by concentration of NaCl, and the water quantity index represented by water elevation are regarded as dependent variables. The salinity threshold of 240 ppt (parts per thousand) is selected as the water quality requirement for Artemia urmiana. Finally, the aggregation of these variables shows that Lake Urmia requires annually 3086 MCM of inflow water to have a sustainable ecosystem.

Balancing agricultural and environmental water needs in China: alternative scenarios and policy options

China is facing growing water scarcity in many river basins due to rapid economic development, an expanding population, growing urbanization, and limited scope to develop new supplies. Water overdrafts, both from surface and sub-surface sources, are causing serious environmental problems ranging from the degradation of deltaic ecosystems of major rivers to aquifer depletion in North China. The attendant need to meet environmental water requirements is exacerbating the already tenuous problem of inter-sectoral water competition. The most widely advocated solution for the present and future environmental water management challenges of China involves the reallocation of water from agriculture to urban and environmental sectors. Such a solution can be myopic, unless potential repercussions on national food production and irrigating farmers are addressed. This paper identifies the role of increased water-use efficiency for enhanced environmental flows, and develops options for balancing environmental and food needs in China based on simulations using an integrated, global water–food projections model.

Estimation of environmental flows in the Great Ruaha River Catchment, Tanzania

For the past eleven years, the Great Ruaha River which flows through the Ruaha National Park has ceased flowing during the dry season, with extended periods of zero flow. The drying up has resulted in social conflicts between upstream and downstream users. It has also caused adverse impacts on the ecosystem of the Ruaha National Park, disrupting the lives of many animals and causing changes in their behaviour. In this paper we present the findings of a hydrological study conducted to estimate environmental flow requirements. The desktop reserve model was used to determine maintenance high and low flows, and drought low flow requirements within the Ruaha National Park. The results indicate that to maintain the basic ecological functioning of the river requires an average allocation of 635.3 Mm 3/a (equivalent to 21.6% of mean annual runoff). This is the average annual maintenance flow; comprising of maintenance low flows (i.e. 15.9% MAR; 465 Mm 3/a) and maintenance high flows (i.e. 5.8% of MAR; 170 Mm 3/a). The absolute minimum water requirement was estimated to be 0.54 m 3/s with the probability of exceedance of 0.99. The study confirms that in the absence of ecological information hydrological indices can be used to provide a first estimate of environmental water requirements. However, before being applied, greater understanding of the relationships between flow and the ecological condition of the riverine ecosystem is required.

A genetic algorithm-based fuzzy multi-objective programming approach for environmental water allocation

A fuzzy multiobjective-programming model was presented to determine appropriate environmental flow allocation in urban rivers. An integrated nonlinear fuzzy membership function, that represents a broader implication in fuzzy decision-making, was regarded as the general objective and genetic algorithm became an essential tool in search for the global optimal solution. A case study of optimal allocation for environmental water requirements in the Liming River Basin, Daqing, demonstrates the capability of the fuzzy multiobjective model based on fuzzy decision theories to work suitably in water environmental management in a river basin.

Progress in ecological and environmental water requirements research and applications in China

: With economic development, as well as population growth, the conflict between water supply and demand has become more and more acute in China, and it has been aggravated further by the irrational utilization of water resources. As a result, the deterioration and destruction of the eco‐environment have become increasingly serious. In order to effectively protect ecosystems and improve their ecological conditions, many studies on ecological and environmental water requirements (EEWR) have been carried out in China. In this paper, the concept and characteristics of EEWR are addressed, and the main advances of EEWR research and applications in China are summarized in four types of systems including studies on rivers, vegetation, lakes and wetlands, and groundwater. In conclusion, issues necessary to be studied further in the future are put forward.

Potential ecological effects of water extraction in small, unregulated streams

River regulation can have various effects on the natural flow regime, however the most obvious and perhaps pronounced hydrological effect is the reduction of total water discharge. Whilst there has been an increasing number of studies investigating the impacts of river regulation on lowland rivers, few studies have specifically investigated the effects of water extractions on small upland streams. In this study, we experimentally examined the effects of short-term, summer water extractions from small, unregulated streams. Five 30 m reaches were experimentally manipulated to divert a proportion of the total stream flow, and another five 30 m reaches were designated as controls, in the Yea River catchment, Victoria, Australia. The percentage of total discharge diverted from each experimental reach varied through time and between creeks (28–97%), with discharge always significantly reduced compared to control locations. All sites were monitored for available habitat, biofilm, water quality and macroinvertebrate diversity and density, fortnightly during February and March 2004. Despite the range of total stream volumes being extracted, the manipulation altered important ecological components of these unregulated creeks, including changes in physical habitat features (reduced stream wetted area and maximum stream depth) and reduced dissolved oxygen concentrations. Biofilm parameters showed a slight increase in diverted reaches, but were not statistically different from the controls. There was no statistical difference in total density of macroinvertebrates or EPT taxa; however, the density of Austrocercella mariannae (Notonemouridae) was significantly reduced in diverted reaches. Macroinvertebrate family level diversity, and the family diversity of grazers and shredders was reduced in diverted reaches. This study demonstrates that there are likely to be significant ecological impacts of extracting water in unregulated creeks. Whilst this study has demonstrated the need to consider environmental water requirements in unregulated streams, further studies are required to inform the debate about the volume, timing and predicted ecological response with improved environmental water. Copyright © 2006 John Wiley & Sons, Ltd.

The use of remote sensing for monitoring environmental indicators: The case of the Incomati estuary, Mozambique

The Incomati river basin is a transboundary basin shared by three countries: South Africa, Mozambique and Swaziland. To assess the water requirements of the environment, as stated in the Tripartite Interim Agreement (TIA) signed by the three riparian countries in Johannesburg in 2002, Mozambique needs to monitor the ecological state of the river, including the estuary. A monitoring system has to be established that can evaluate the environmental fresh water requirements based on appropriate indicators that reflect the health of the Incomati estuary. The estuary of the Incomati has important ecological functions but it also is an important socio-economic resource. Local communities depend on the estuary’s natural resources. Modifications of the river flow regime by upstream developments impact on the productivity of the estuary, diminishing fish and shrimp production, reducing biomass of natural vegetation such as grasses, reeds and mangroves and increasing salt intrusion. A decrease in estuary productivity consequently affects the incomes and living conditions of these communities. Based on an understanding of the effects of different pressures on the estuary ecosystem some indicators for monitoring the environmental state of the estuary are suggested, including the extent and vitality of mangrove forests. This latter indicator is further elaborated in the paper. Remote sensing techniques were used to identify and quantify mangrove forests in two selected areas of the estuary (Xefina Pequeña Island and Benguelene Island). Five satellite images covering a period of 20 years (1984–2003) showed that the area covered by non-degraded mangroves significantly decreased on both islands, by 25% in Xefina Pequeña Island and 40% in Benguelene Island. Moreover, the study of biomass reflection using NDVI also showed a significant decline in biomass densities over the last 20 years. Possible causes of these changes are reviewed: natural rainfall trends, modifications of the river flow regime, and increasing harvesting levels of mangrove woods. The findings presented in this paper show that mangrove forests are relevant indicators of the state of the estuary, which can be assessed by means of remote sensing techniques. Follow-up research is required that will establish the relative importance of the causal factors on the vitality of the estuarine mangrove forests. It is concluded that remotely sensed images may provide important data for an environmental monitoring system.

Review of Namibian legislation and policies pertinent to environmental flows

The rationale for evaluating Namibian environmental flows is essentially that of ensuring ‘the maintenance of ecosystems, essential ecological processes and biological diversity’ and the sustainable utilisation of natural resources as promoted in clause 95 of the Namibian Constitution. Recent policy and legislative reforms have created a unique opportunity for Namibia to incorporate environmental sensitivity clauses such as those to ensure adequate environmental flows for river systems. The Second National Development Plan and the National Water Policy White Paper form the basis for the new Water Resources Management Act, promulgated in December 2004. The National Water Policy includes a basic principle headed “Ecosystem values and sustainability” that stresses that the management of water resources needs to harmonise human and environmental requirements, recognising the role of water in supporting the ecosystem. One of the strategies given to ensure environmental and economic sustainability reads: “Ensure that in-stream flows are adequate both in terms of quality and quantity to sustain the ecosystem”. Although the water policy clearly states that: “The legislation will provide for determining an environmental water reserve for freshwater sources before they can be used to supply other demands than domestic and subsistence livestock watering”, there is now no direct mention of environmental flows in the new Water Act. This paper explores to what extent the need for the determination of environmental water needs has been incorporated into Namibian policies, legislation and development plans. It makes recommendations, pertinent to the Namibian situation, of what needs to be done to ensure that environmental water requirements are taken into account in future planning, operation and management of Namibia’s precious water resources.

Hydrological issues associated with the determination of environmental water requirements of ephemeral rivers

The paper reviews the generic characteristics of ephemeral rivers compared with seasonal and perennial systems in the context of southern Africa. The difficulties of estimating the natural characteristics of ephemeral systems are discussed as well as the difficulties of estimating the impacts of water resource management strategies. Many of the problems are associated with the potentially discontinuous occurrence of flow in both time and space and the fact that static pools, as well as flowing water, may be of ecological importance. The most obvious impact of water resource developments on ephemeral rivers may be a reduction in the number and size of flow events. However, delays in the onset of flow in seasonal rivers and changes in the duration, quantity and quality of in-channel pool storage may be of equal importance. In a number of South African ephemeral channels the major impacts have been caused by the importation of water from elsewhere and a consequent reduction in streamflow variability. The paper suggests that there are a number of gaps in the understanding of the hydrology of ephemeral rivers, but perhaps more importantly, in the methods that are available to supply the type of information required by ecological specialists to be able to determine ecological water requirements under managed flow situations. Copyright © 2005 John Wiley & Sons, Ltd.

A Pilot Global Assessment of Environmental Water Requirements and Scarcity

This paper presents a first attempt to estimate the volume of water required for the maintenance of freshwater-dependent ecosystems at the global scale. This total environmental water requirement consists of ecologically relevant low-flow and high-flow components and depends upon the objective of environmental water management. Both components are related to river flow variability and estimated by conceptual rules from discharge time series simulated by the global hydrology model. A water stress indicator is further defined, which shows what proportion of the utilizable water in world river basins is currently withdrawn for direct human use and where this use is in conflict with environmental water requirements. The paper presents an estimate of environmental water requirements for 128 major river basins and drainage regions of the world. It is shown that approximately 20 to 50 percent of the mean annual river flow in different basins needs to be allocated to freshwater-dependent ecosystems to maintain them in fair conditions. This is unlikely to be possible in many developing countries in Asia and North Africa, in parts of Australia, North America, and Europe, where current total direct water withdrawals (primarily for irrigation) already tap into the estimated environmental water requirements. Over 1.4 billion people currently live in river basins with high environmental water stress. This number will increase as water withdrawals grow and if environmental water allocations remain beyond the common practice in river basin management. This paper suggests that estimates of environmental water requirements should be the integral part of global water assessments and projections of global food production.

Optional water development strategies for the Yellow River Basin: Balancing agricultural and ecological water demands

The Yellow River Basin is of the utmost importance for China in terms of food production, natural resources management, and socioeconomic development. Water withdrawals for agriculture, industry, and households in the past decade have seriously depleted environmental and ecological water requirements in the basin. This study presents a modeling scenario analysis of some water development strategies to harmonize water withdrawal demand and ecological water demand in the Yellow River Basin through water savings and interbasin water transfers. A global water and food analysis model including the Yellow River Basin as one of the modeling units is applied for the analysis. The model demonstrates that there is little hope of resolving the conflict between agriculture water demand and ecological water demand in the basin if the current water use practices continue. Trade‐offs exist between irrigation water use and ecological water use, and these trade‐offs will become more intense in future years with population growth, urbanization, and industrial development as well as growing food demand. Scenario analysis in this study concludes that increasing basin water use efficiency to 0.67 first and then supplementary water availability by interbasin water transfer through the South‐North Water Transfer Project may provide a solution to water management of the Yellow River Basin in the next 25 years.