Jochen Froebrich

Using participatory modelling to compensate for data scarcity in environmental planning: A case study from India

Participatory modelling has provided a new approach to overcome the problem of data scarcity which formerly interfered with the environmental planning for the restoration of the Kolleru-Upputeru wetland ecosystem on the east coast of Andhra Pradesh in South India. New ways had to be found to address the shortcomings of traditionally validated simulation models. The traditional validation process was replaced by joint plausibility discussions and shared vision building in order to improve the understanding of cause-effect relationships and proposals for restoration measures. This study has aimed to match the tacit knowledge of the local stakeholders with explicit scientific knowledge in order to create (i) a mutual basis for an integrated approach as opposed to single-issue measures and (ii) a mutual agreement on follow-up steps needed to sustain both the livelihood of the people as well as the wetland ecosystem. The challenge was to address the hydrological and social complexity. On the basis of a literature review, input data for model simulations were generated from the location-specific knowledge of stakeholders and a rapid field appraisal. The model simulations were used to predict the effects of a number of restoration options. In two workshops, these restoration options were discussed with the stakeholders in order to improve the mutual understanding of the complexity of the wetland system and to reach an agreement on the outlines of an integrated action plan. The participatory modelling approach proved to be a useful tool to obtain a consensus of opinions among the stakeholders.

Evaluation of the SWAT Model for Assessing Sediment Control Structures in a Small Watershed in India

Stormwater runoff is a major pathway for transporting sediment and other nonpoint-source pollutants from watersheds to stream systems and other surface water bodies. In this study, the Soil and Water Assessment Tool (SWAT) model was used to assess sediment transport from the 17 km2 Banha watershed located in northeast India, which is characterized by mixed land use and on-stream sediment control structures called checkdams. Calibration (1996) and validation (1997-2001) of surface runoff and sediment yield were performed with SWAT on both a daily and monthly basis by comparing model estimates versus measured data. The calibration R2 and Nash-Sutcliffe modeling efficiency (NSE) statistics were found to range between 0.70 to 0.99 for surface runoff and 0.82 to 0.98 for sediment loss. The corresponding validation period statistics ranged from 0.60 to 0.92 for surface runoff and 0.58 to 0.89 for sediment loss. Following calibration and validation, the SWAT model was executed with and without checkdams to test its capability in visualizing the impacts of sediment control structures in the watershed. The model estimates showed that sediment loss from the watershed could be reduced more than 64% by adopting checkdams as a barrier for sediment. The results also revealed the potential for using SWAT to assess sediment transport from specific subwatersheds within a watershed, and to prioritize the siting of sediment control structures within a watershed to obtain the most effective reduction of sediment losses to surface water. Overall, the study showed that SWAT can be a useful tool for studying how checkdams can be used to manage and control sediment loss from small watersheds located in sub-humid climate conditions.

Spatial variability of climate change impacts on yield of rice and wheat in the Indian Ganga Basin

Indian Ganga Basin (IGB), one of the most densely populated areas in the world, is facing a significant threat to food grain production, besides increased yield gap between actual and potential production, due to climate change. We have analyzed the spatial variability of climate change impacts on rice and wheat yields at three different locations representing the upper, middle and lower IGB. The DSSAT model is used to simulate the effects of climate variability and climate change on rice and wheat yields by analyzing: (i) spatial crop yield response to current climate, and (ii) impact of a changing climate as projected by two regional climate models, REMO and HadRM3, based on SRES A1B emission scenarios for the period 2011-2040. Results for current climate demonstrate a significant gap between actual and potential yield for upper, middle and lower IGB stations. The analysis based on RCM projections shows that during 2011-2040, the largest reduction in rice and wheat yields will occur in the upper IGB (reduction of potential rice and wheat yield respectively by 43.2% and 20.9% by REMO, and 24.8% and 17.2% by HadRM3). In the lower IGB, however, contrasting results are obtained, with HadRM3 based projections showing an increase in the potential rice and wheat yields, whereas, REMO based projections show decreased potential yields. We discuss the influence of agro-climatic factors; variation in temperature, length of maturity period and leaf area index which are responsible for modeled spatial variability in crop yield response within the IGB.

Investigating hydrological regimes and processes in a set of catchments with temporary waters in Mediterranean Europe

Abstract Seven catchments of diverse size in Mediterranean Europe were investigated in order to understand the main aspects of their hydrological functioning. The methods included the analysis of daily and monthly precipitation, monthly potential evapotranspiration rates, flow duration curves, rainfall—runoff relationships and catchment internal data for the smaller and more instrumented catchments. The results showed that the catchments were less “dry” than initially considered. Only one of them was really semi-arid throughout the year. All the remaining catchments showed wet seasons when precipitation exceeded potential evapotrans-piration, allowing aquifer recharge, “wet” runoff generation mechanisms and relevant baseflow contribution. Nevertheless, local infiltration excess (Hortonian) overland flow was inferred during summer storms in some catchments and urban overland flow in some others. The roles of karstic groundwater, human disturbance and low winter temperatures were identified as having an important impact on the hydrological regime in some of the catchments.

River flow regime and snow cover of the Pamir Alay (Central Asia) in a changing climate

Abstract The Vakhsh and Pyandj rivers, main tributaries of the Amu Darya River in the mountainous region of the Pamir Alay, play an important role in the water resources of the Aral Sea basin (Central Asia). In this region, the glaciers and snow cover significantly influence the water cycle and flow regime, which could be strongly modified by climate change. The present study, part of a project funded by the European Commission, analyses the hydrological situation in six benchmark basins covering areas of between 1800 and 8400 km2, essentially located in Tajikistan, with a variety of topographical situations, precipitation amounts and glacierized areas. Four types of parameter are discussed: temperature, glaciation, snow cover and river flows. The study is based mainly on a long-time series that ended in the 1990s (with the collapse of the Soviet Union) and on field observations and data collection. In addition, a short, more recent period (May 2000 to May 2002) was examined to better understand the role of snow cover, using scarce monitored data and satellite information. The results confirm the overall homogeneous trend of temperature increase in the mountain range and its impacts on the surface water regime. Concerning the snow cover, significant differences are noted in the location, elevation, orientation and morphology of snow cover in the respective basins. The changes in the river flow regime are regulated by the combination of the snow cover dynamics and the increasing trend of the air temperature. Editor Z.W. Kundzewicz Citation Chevallier, P., Pouyaud, B., Mojaïsky, M., Bolgov, M., Olsson, O., Bauer, M., and Froebrich, J., 2014. River flow regime and snow cover of the Pamir Alay (Central Asia) in a changing climate. Hydrological Sciences Journal, 59 (8), 1491–1506. http://dx.doi.org/10.1080/02626667.2013.838004

Flood generation and classification of a semi-arid intermittent flow watershed: Evrotas river

Hourly water level measurements were used to investigate the flood characteristics of a semi-arid river in Greece, the Evrotas. Flood events are analysed with respect to flood magnitude and occurrence and the performance of Curve Number approach over a period of 2007–2011. A distributed model, Soil and Water Assessment Tool, is used to simulate the historic floods (1970–2010) from the available rainfall data, and the performance of the model assessed. A new flood classification method was suggested the Peaks-Duration Over Threshold method that defines three flood types: ‘usual’, ‘ecological’ and ‘hazardous’. We classify the basin according to the flood type for the most serious past simulated flood events. The proportion of hazardous floods in the main stream is estimated to be 5–7% with a lower figure in tributaries. Flood Status Frequency Graphs and radar plots are used to show the seasonality of simulated floods. In the Evrotas, the seasonality pattern of hazardous flood is in agreement with other studies in Greece and differs from other major European floods. The classification in terms of flood types in combination with flood type seasonality is identified as an important tool in flood management and restoration.

Simulating streamflow variability and aquatic states in temporary streams using a coupled groundwater-surface water model

Abstract In order to apply the EU Water Framework Directive for temporary streams, it is important to quantify the space–time development of different aquatic states. We report on research on the development of aquatic states for temporary streams in the Evrotas basin, Greece. The SIMGRO regional hydrological model was used in a GIS framework to generate flow time series for the Evrotas River and all major tributaries. Five flow phases were distinguished: flood conditions, riffles, connected pools, isolated pools and dry bed conditions. Thresholds based on local hydraulic characteristics were identified per stream reach and flow phase, enabling the frequency of flow phases per month and the average frequencies for all streams to be derived. Three historical scenarios within the 20th century, marking periods of major changes in water management, were investigated. Additionally, a climate scenario for the 2050s was analysed. Simulations revealed that low flows are now much lower, mainly because more groundwater is abstracted for irrigation. The consequence is that stretches of the river fall dry during several months, causing the ecological status to deteriorate. Editor Z.W. Kundzewicz Associate editor X. Chen