Systems Analysis, Integrated Assessment and Modelling
In SIAM, we develop and apply models and formal techniques in order to understand, demonstrate, and predict the behavior of natural, technical, social and economical systems that pertain to water and other natural resources. Read more
Towards improvement of grey water footprint assessment: With an illustration for global maize cultivation
The grey water footprint refers to the volume of water that is required to assimilate polluted water. It reflects the intensity of water pollution caused by water use for human activities. This study aims to address some major shortcomings associated with grey water footprint accounting in the literature and discuss several ways towards its improvement. Global maize production is used for illustration. The study specifically tackles three issues: the appropriate water quality standards for grey water footprint assessment; grey water footprint for multiple pollutants; and the influence of spatial resolution of the assessment on the level of grey water stress. A biophysical crop model is applied to quantify nitrogen and phosphorus losses to water in maize production on a global scale with a 0.5-degree spatial resolution. The study shows that the grey water footprint calculation is highly sensitive to the water standards applied. The results also suggest that the grey water footprint relating to nitrogen and phosphorus pollution caused by maize production alone has already exceeded their local water availability in many parts of the world. Grey water stress shows a more critical situation at the grid level than at the watershed level for maize cultivation because the former represents the local concentration whereas the latter gives the average situation of the whole watershed. This study highlights the need for standardizing the setting of water quality standards for a consistent grey water footprint assessment taking into consideration the diverse aquatic ecosystems and ambient water quality requirements across regions, as well as the presence of multiple pollutants in water bodies.
Modeling crop water productivity using a coupled SWAT–MODSIM model
This study examines the water productivity of irrigated wheat and maize yields in Karkheh River Basin (KRB) in the semi-arid region of Iran using a coupled modeling approach consisting of the hydrological model (SWAT) and the river basin water allocation model (MODSIM). Dynamic irrigation requirements instead of constant time series of demand were considered. As the cereal production of KRB plays a major role in supplying the food market of Iran, it is necessary to understand the crop yield-water relations for irrigated wheat and maize in the lower part of KRB (LKRB) where most of the irrigated agricultural plains are located. Irrigated wheat and maize yields (Y) and consumptive water use (AET) were modeled with uncertainty analysis at a subbasin level for 1990–2010. Simulated Y and AET were used to calculate crop water productivity (CWP). The coupled SWAT–MODSIM approach improved the accuracy of SWAT outputs by considering the water allocation derived from MODSIM. The results indicated that the highest CWP across this region was 1.31 kg·m−3 and 1.13 kg·m−3 for wheat and maize, respectively; and the lowest was less than 0.62 kg·m−3 and 0.58 kg·m−3. A close linear relationship was found for CWP and yield. The results showed a continuing increase for AET over the years while CWP peaks and then declines. This is evidence of the existence of a plateau in CWP as AET continues to increase and evidence of the fact that higher AET does not necessarily result in a higher yield.
Uncertainty based assessment of dynamic freshwater scarcity in semi-arid watersheds of Alberta, Canada
Study region: Alberta, Canada. Study focus: The security of freshwater supplies is a growing concern worldwide. Understanding dynamics of water supply and demand is the key for sustainable planning and management of watersheds. Here we analyzed the uncertainties in water supply of Alberta by building an agro-hydrological model, which accounts for major hydrological features, geo-spatial heterogeneity, and conflicts over water-food-energy resources. We examined the cumulative effects of natural features (e.g., potholes, glaciers, climate, soil, vegetation), anthropogenic factors (e.g., dams, irrigation, industrial development), environmental flow requirements (EFR), and calibration schemes on water scarcity in the dynamics of blue and green water resources, and groundwater recharge. New hydrological insights for the region: Natural hydrologic features of the region create a unique hydrological system, which must be accurately represented in the model for reliable estimates of water supply at high spatial and temporal resolution. Accounting for EFR, increases the number of months of water scarcity and the population exposed. Severe blue water scarcity in spring and summer months was found to be due to irrigated agriculture, while in winter months it was mostly due to the demands of petroleum or other industries. We found over exploitation of the groundwater in southern subbasins and concluded that more detailed analysis on groundwater flow and connectivity is required. Our study provides a general and unified approach for similar analyses in other jurisdictions around the world.
Faramarzi,M.; Abbaspour,K.C.; W.L. (Vic) Adamowiczc, Wei Luc, Jon Fennelld,J.; Zehnder,A.J.B.; Goss,G.G. (2017) Uncertainty based assessment of dynamic freshwater scarcity in semi-arid watersheds of Alberta, Canada, Journal of Hydrology: Regional Studies, 9, 48-68, doi:10.1016/j.ejrh.2016.11.003, Institutional Repository
Burden shifting of water quantity and quality stress from megacity Shanghai
Much attention has been paid to burden shifting of CO2 emissions from developed regions to developing regions through trade. However, less discussed is that trade also acts as a mechanism enabling wealthy consumers to shift water quantity and quality stress to their trading partners. In this study, we investigate how Shanghai, the largest megacity in China, draws water resources from all over China and outsources its pollution through virtual quantity and quality water flows associated with trade. The results show that Shanghai's consumption of goods and services in 2007 led to 11.6 billion m3 of freshwater consumption, 796 thousand tons of COD, and 16.2 thousand tons of NH3-N in discharged wastewater. Of this, 79% of freshwater consumption, 82.9% of COD and 82.5% of NH3-N occurred in other Chinese Provinces which provide goods and services to Shanghai. Thirteen Provinces with severe and extreme water quantity stress accounted for 60% of net virtual water import to Shanghai, while 19 Provinces experiencing water quality stress endured 79% of net COD outsourcing and 75.5% of net NH3-N outsourcing from Shanghai. In accordance with the three “redlines” recently put forward by the Chinese central government to control water pollution and cap total water use in all provinces, we suggest that Shanghai should share its responsibility for reducing water quantity and quality stress in its trading partners through taking measures at provincial, industrial, and consumer levels. In the meantime, Shanghai needs to enhance demand side management by promoting low water intensity consumption.
Integrating and extending ecological river assessment: Concept and test with two restoration projects
While the number of river restoration projects is increasing, studies on their success or failure relative to expectations are still rare. Only a few decision support methodologies and integrative methods for evaluating the ecological status of rivers are used in river restoration projects, thereby limiting informed management decisions in restoration planning as well as success control. Moreover, studies quantifying river restoration effects are often based on the assessment of a single organism group, and the effects on terrestrial communities are often neglected. In addition, potential effects of water quality or hydrological degradation are often not considered for the evaluation of restoration projects. We used multi-attribute value theory to re-formulate an existing river assessment protocol and extend it to a more comprehensive, integrated ecological assessment program. We considered habitat conditions, water quality regarding nutrients, micropollutants and heavy metals, and five instream and terrestrial organism groups (fish, benthic invertebrates, aquatic vegetation, ground beetles and riparian vegetation). The physical, chemical and biological states of the rivers were assessed separately and combined to value the overall ecological state. The assessment procedure was then applied to restored and unrestored sites at two Swiss rivers to test its feasibility in quantifying the effect of river restoration. Uncertainty in observations was taken into account and propagated through the assessment framework to evaluate the significance of differences between the ecological states of restored and unrestored reaches. In the restored sites, we measured a higher width variability of the river, as well as a higher width of the riparian zone and a higher richness of organism groups. According to the ecological assessment, the river morphology and the biological states were significantly better at the restored sites, with the largest differences detected for ground beetles and fish communities, followed by benthic invertebrates and riparian vegetation. The state of the aquatic vegetation was slightly lower at the restored sites. According to our assessment, the presence of invasive plant species counteracted the potential ecological gain. Water quality could be a causal factor contributing to the absence of larger improvements. Overall, we found significantly better biological and physical states, and integrated ecological states at the restored sites. Even in the absence of comprehensive before-after data, based on the similarity of the reaches before restoration and mechanistic biological knowledge, this can be safely interpreted as a causal consequence of restoration. An integrative perspective across aquatic and riparian organism groups was important to assess the biological effects, because organism groups responded differently to restoration. In addition, the potential deteriorating effect of water quality demonstrates the importance of integrated planning for the reduction of morphological, water quality and hydrological degradation.
The water footprint indicates how much water is used to produce consumer goods. A study by Eawag scientists shows that there is a need for standardization in assessments of the grey water component. Comparability is impaired, for example, by the use of different water quality standards. Read more