Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.

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Climate Change 2007: The Physical Science Basis.

Impatti, adattamento e vulnerabilita Le cause e le responsabilita dei cambiamenti climatici sono state trattate sul numero di ottobre della rivista Cda. Approfondiamo l’argomento presentando il documento: “Cambiamenti climatici 2007: impatti, adattamento e vulnerabilita” votato ad aprile 2007 dal secondo gruppo di lavoro del Comitato Intergovernativo sui Cambiamenti Climatici (Intergovernmental Panel on Climate Change). Si tratta del secondo di tre documenti che compongono il quarto rapporto sui cambiamenti climatici.

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Climate Change 2007: Impacts, Adaptation and Vulnerability.

The Soil and Water Assessment Tool (SWAT) model is a continuation of nearly 30 years of modeling efforts conducted by the USDA Agricultural Research Service (ARS). SWAT has gained international acceptance as a robust interdisciplinary watershed modeling tool as evidenced by international SWAT conferences, hundreds of SWAT-related papers presented at numerous other scientific meetings, and dozens of articles published in peer-reviewed journals. The model has also been adopted as part of the U.S. Environmental Protection Agency (USEPA) Better Assessment Science Integrating Point and Nonpoint Sources (BASINS) software package and is being used by many U.S. federal and state agencies, including the USDA within the Conservation Effects Assessment Project (CEAP). At present, over 250 peer-reviewed published articles have been identified that report SWAT applications, reviews of SWAT components, or other research that includes SWAT. Many of these peer-reviewed articles are summarized here according to relevant application categories such as streamflow calibration and related hydrologic analyses, climate change impacts on hydrology, pollutant load assessments, comparisons with other models, and sensitivity analyses and calibration techniques. Strengths and weaknesses of the model are presented, and recommended research needs for SWAT are also provided.

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The Soil and Water Assessment Tool: Historical Development, Applications, and Future Research Directions

The Soil and Water Assessment Tool (SWAT) model is a continuation of nearly 30 years of modeling efforts conducted by the U.S. Department of Agriculture (USDA), Agricultural Research Service. SWAT has gained international acceptance as a robust interdisciplinary watershed modeling tool, as evidenced by international SWAT conferences, hundreds of SWAT-related papers presented at numerous scientific meetings, and dozens of articles published in peer-reviewed journals. The model has also been adopted as part of the U.S. Environmental Protection Agency's BASINS (Better Assessment Science Integrating Point & Nonpoint Sources) software package and is being used by many U.S. federal and state agencies, including the USDA within the Conservation Effects Assessment Project. At present, over 250 peer-reviewed, published articles have been identified that report SWAT applications, reviews of SWAT components, or other research that includes SWAT. Many of these peer-reviewed articles are summarized here according to relevant application categories such as streamflow calibration and related hydrologic analyses, climate change impacts on hydrology, pollutant load assessments, comparisons with other models, and sensitivity analyses and calibration techniques. Strengths and weaknesses of the model are presented, and recommended research needs for SWAT are provided.

Soil and Water Assessment Tool: Historical Development, Applications, and Future Research Directions, The

SWAT (Soil and Water Assessment Tool) is a comprehensive, semi-distributed river basin model that requires a large number of input parameters, which complicates model parameterization and calibration. Several calibration techniques have been developed for SWAT, including manual calibration procedures and automated procedures using the shuffled complex evolution method and other common methods. In addition, SWAT-CUP was recently developed and provides a decision-making framework that incorporates a semi-automated approach (SUFI2) using both manual and automated calibration and incorporating sensitivity and uncertainty analysis. In SWAT-CUP, users can manually adjust parameters and ranges iteratively between autocalibration runs. Parameter sensitivity analysis helps focus the calibration and uncertainty analysis and is used to provide statistics for goodness-of-fit. The user interaction or manual component of the SWAT-CUP calibration forces the user to obtain a better understanding of the overall hydrologic processes (e.g., baseflow ratios, ET, sediment sources and sinks, crop yields, and nutrient balances) and of parameter sensitivity. It is important for future calibration developments to spatially account for hydrologic processes; improve model run time efficiency; include the impact of uncertainty in the conceptual model, model parameters, and measured variables used in calibration; and assist users in checking for model errors. When calibrating a physically based model like SWAT, it is important to remember that all model input parameters must be kept within a realistic uncertainty range and that no automatic procedure can substitute for actual physical knowledge of the watershed.

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SWAT: Model Use, Calibration, and Validation

http://www.nurserycropscience.info/water/managing-runoff/technical-pubs/reichenberger-et-al.-2007.-mitigation-strategies-to-reduce-pesticide-inputs-into-ground-and-surface-water-and-their-effectiveness-a-review

Mitigation strategies to reduce pesticide inputs into ground- and surface water and their effectiveness; A review

Due to spatial variability, budget constraints or access difficulties model input parameters always are uncertain to some extent. Therefore the knowledge of sensitive input parameters is beneficial for model development and application. It can lead to a better understanding and to better estimated values and thus reduced uncertainty. In the present paper two simple approaches of sensitivity analysis are compared by the use of the physically based, continuous time hydrological model SWAT. In both approaches, one parameter is varied at a time while holding the others fixed, but the way of defining the range of variation is different. Similar results are obtained suggesting that parameter sensitivity may be determined without the results being influenced by the chosen method. Most sensitive parameters for hydrology and water quality are the physical soil properties such as bulk density, available water capacity or hydraulic conductivity. Plant specific parameters like maximum stomatal conductance or maximum leaf area index as well as slope length, slope steepness, and curve number also show a high sensitivity. Both approaches can be considered as equivalent, as they provide the same overall ranking into more and less sensitive parameters. An identification of the sensitive parameters is possible independently from the chosen variation range.

Comparison of two different approaches of sensitivity analysis

Regional land use changes due to European market policy have far reaching consequences for various landscape functions. Among others land use change influences the local water balance. Simulation models are mostly used to analyse the effect of management practices on water quality but they can also be a useful tool to quantify the hydrologic response of a catchment to different land use options. In this study the physically based, continuous time step model SWAT mod has been applied within the joint research project SFB 299 at the Giessen University to support the development of sustainable land use concepts. In a first step the model has been calibrated and validated for four mesoscale watersheds with differing land use distributions. Then the model performance for changing land use has been tested in an artificial watershed with a single crop at one time and one underlying soil type to eliminate the complex interactions of natural watersheds. In relation to forest barley produced the strongest response of the water balance components. Finally a case study for the Dietzholze watershed with two land use scenarios derived with the ProLand model has been carried out. The impact of land use change on the annual water balance was relatively small due to compensating effects in a complex catchment. The decrease of forest due to a grassland bonus amplifies the peak flow rate and thus increases the risk of flooding.

Hans-Georg Frede

Papers

Mitigation strategies to reduce pesticide inputs into ground- and surface water and their effectiveness; A review

Comparison of two different approaches of sensitivity analysis

Hydrologic Response to land use changes on the catchment scale

Plant parameter values for models in temperate climates

Parameter uncertainty and the significance of simulated land use change effects