Quantifying the impact of model inaccuracy in climate change impact assessment studies using an agro-hydrological model

Numerical simulation models are frequently applied to assess the impact of climate change on hydrology and agriculture. A common hypothesis is that unavoidable model errors are reflected in the reference situation as well as in the climate change situation so that by comparing reference to scenario model errors will level out. For a polder in The Netherlands an innovative procedure has been introduced, referred to as the Model-Scenario-Ratio (MSR), to express model inaccuracy on climate change impact assessment studies based on simulation models comparing a reference situation to a climate change situation. The SWAP (Soil Water Atmosphere Plant) model was used for the case study and the reference situation was compared to two climate change scenarios. MSR values close to 1, indicating that impact assessment is mainly a function of the scenario itself rather than of the quality of the model, were found for most indicators evaluated. A climate change scenario with enhanced drought conditions and indicators based on threshold values showed lower MSR values, indicating that model accuracy is an important component of the climate change impact assessment. It was concluded that the MSR approach can be applied easily and will lead to more robust impact assessment analyses

Regionale waterberging in Noord-Brabant

Voor het thema waterberging van de reconstructie in Noord-Brabant is een instrument gemaakt om de zoekruimte voor waterberging in het regionale watersysteem te kwantificeren. Dit Hoogwater Instrument Brabant (HIB) is een ARCVIEW-applicatie rond het integrale watersysteemmodel SIMGRO en rekent met stochasten conform de hoogwaternormering regionale watersystemen. Het instrument gaat uit van beschikbare digitale databestanden. Essentieel zijn de leggergegevens van de waterschappen, HIB voert controles op consistentie uit en controleert deze data. HIB is door adviesbureaus en door waterschappen toegepast om modellen te bouwen om de zoekruimte voor waterberging te bepalen. Het gebruiksgemak en de opzet van HIB maken dat dit instrument geschikt is als instrument voor waterschappen om de vragen waterbeheer integraal te onderbouwe

Прогнозирование временного сопротивления разрыву малоуглеродистой низколегированной арматурной стали на основе системы частных регрессионных моделей

Предложен способ декомпозиции многофакторной регрессионной модели прогнозирования механических свойств арматурного проката. Обоснована система частных регрессионных моделей прогнозирования временного сопротивления разрыву арматурного проката. Показано, что полученные результаты хорошо согласуются с экспериментальными данными

№ 107. Додаткове свідчення Миколи Чехівського від 27 вересня 1929 р.

In the headwater catchments of the main Asian rivers, glaciohydrological models are a useful tool to anticipate impacts of climatic changes. However, the reliability of their projections strongly depends on the quality and quantity of data that are available for parameter estimation, model calibration and validation, as well as on the accuracy of climate change projections. In this study the physically oriented, glaciohydrological model TOPKAPI-ETH is used to simulate future changes in snow, glacier, and runoff from the Hunza River Basin in northern Pakistan. Three key sources of model uncertainty in future runoff projections are compared: model parameters, climate projections, and natural climate variability. A novel approach, applicable also to ungauged catchments, is used to determine which model parameters and model components significantly affect the overall model uncertainty. We show that the model is capable of reproducing streamflow and glacier mass balances, but that all analyzed sources of uncertainty significantly affect the reliability of future projections, and that their effect is variable in time and in space. The effect of parametric uncertainty often exceeds the impact of climate uncertainty and natural climate variability, especially in heavily glacierized subcatchments. The results of the uncertainty analysis allow detailed recommendations on network design and the timing and location of field measurements, which could efficiently help to reduce model uncertainty in the future

Análisis de la variabilidad espacial y temporal de la precipitación en la provincia de Tungurahua, Ecuador, para una mejor planificación agrícola

En este estudio se presentan datos de la distribución espacial de las precipitaciones y las tendencias en la provincia de Tungurahua, Ecuador, a partir de un refinamiento de métodos científicamente probados. Se combinaron datos de las estaciones meteorológicas con datos de teledetección para conocer mejor la distribución espacial de la precipitación en las zonas donde se carece de observaciones directas y donde se quiere promover y modernizar la agricultura. La cantidad total de la precipitación en la cuenca varía desde alrededor de 500 mm/año en torno a Ambato hasta 4000 mm en el sureste de la provincia y se concluye que tanto la variabilidad temporal como la espacial son muy significativas. La media anual para toda la provincia oscila entre 1400 y 1700 mm. La zona más seca es también la zona con mayor variabilidad en el tiempo, coincidiendo con la zona principal agrícola. El régimen pluvial permite aquí cultivos de ciclo corto, lo que refleja la situación actual. Los cultivos plurianuales se producen en las zonas con una mayor precipitación y con menor variabilidad temporal. La comparación entre las observaciones y los valores obtenidos mediante el método indican una buena correlación. Se ha llevado a cabo una validación cruzada de las salidas del algoritmo para determinar en qué zonas la predicción es mejor o peor. En general se concluye que el método utilizado es muy útil, los resultados son satisfactorios y aplicables en otros lugares

Climate change impacts on the Upper Indus hydrology : sources, shifts and extremes

This study was undertaken under the Indus Basin Programme of ICIMOD, funded in part by the United Kingdom's Department for International Development (DFID), through their financial support of core research at ICIMOD. This work is partly carried out by the Himalayan Adaptation, Water and Resilience (HI-AWARE) consortium under the Collaborative Adaptation Research Initiative in Africa and Asia (CARIAA) with financial support from the United Kingdom's Department for International Development (DFID) and the International Development Research Centre (IDRC), Ottawa, Canada.The Indus basin heavily depends on its upstream mountainous part for the downstream supply of water while downstream demands are high. Since downstream demands will likely continue to increase, accurate hydrological projections for the future supply are important. We use an ensemble of statistically downscaled CMIP5 General Circulation Model outputs for RCP4.5 and RCP8.5 to force a cryospheric-hydrological model and generate transient hydrological projections for the entire 21st century for the upper Indus basin. Three methodological advances are introduced: (i) A new precipitation dataset that corrects for the underestimation of high-altitude precipitation is used. (ii) The model is calibrated using data on river runoff, snow cover and geodetic glacier mass balance. (iii) An advanced statistical downscaling technique is used that accounts for changes in precipitation extremes. The analysis of the results focuses on changes in sources of runoff, seasonality and hydrological extremes. We conclude that the future of the upper Indus basin's water availability is highly uncertain in the long run, mainly due to the large spread in the future precipitation projections. Despite large uncertainties in the future climate and long-term water availability, basin-wide patterns and trends of seasonal shifts in water availability are consistent across climate change scenarios. Most prominent is the attenuation of the annual hydrograph and shift from summer peak flow towards the other seasons for most ensemble members. In addition there are distinct spatial patterns in the response that relate to monsoon influence and the importance of meltwater. Analysis of future hydrological extremes reveals that increases in intensity and frequency of extreme discharges are very likely for most of the upper Indus basin and most ensemble members

Impact of debris cover on glacier ablation and atmosphere - glacier feedbacks in the Karakoram

This work was partly carried out under the Collaborative Adaptation Research Initiative in Africa and Asia (CARIAA) with financial support from the UK Government’s Department for International Development and the International Development Research Centre, Ottawa, Canada.The Karakoram range of the Hindu-Kush Himalaya is characterized by both extensive glaciation and a widespread prevalence of surficial debris cover on the glaciers. Surface debris exerts a strong control on glacier surface-energy and mass fluxes and, by modifying surface boundary conditions, has the potential to alter atmosphere– glacier feedbacks. To date, the influence of debris on Karakoram glaciers has only been directly assessed by a small number of glaciological measurements over short periods. Here, we include supraglacial debris in a high-resolution, interactively coupled atmosphere–glacier modeling system. To investigate glaciological and meteorological changes that arise due to the presence of debris, we perform two simulations using the coupled model from 1 May to 1 October 2004: one that treats all glacier surfaces as debris-free and one that introduces a simplified specification for the debris thickness. The basin-averaged impact of debris is a reduction in ablation of 14 %, although the difference exceeds 5mw:e: on the lowest-altitude glacier tongues. The relatively modest reduction in basin-mean mass loss results in part from non-negligible sub-debris melt rates under thicker covers and from compensating increases in melt under thinner debris, and may help to explain the lack of distinct differences in recent elevation changes between clean and debriscovered ice. The presence of debris also strongly alters the surface boundary condition and thus heat exchanges with the atmosphere; near-surface meteorological fields at lower elevations and their vertical gradients; and the atmospheric boundary layer development. These findings are relevant for glacio-hydrological studies on debris-covered glaciers and contribute towards an improved understanding of glacier behavior in the Karakoram

Spatial modelling of mountainous basins; An integrated analysis of the hydrological cycle, climate change and agriculture

Water is the most essential substance on earth and a changing climate has an important impact on the temporal and spatial distribution of water availability. Mountain ranges provide an important “water tower' function and over 20% of the global population depends on fresh water resources provided by the Himalayan range in critical periods of the year. The hydrological cycle is more intense in mountains. Mountains are also more vulnerable to climate change due the dependence of the surface hydrology on snow and ice melt, which directly responds to temperature increases. Although great advances have been made over the last decades in measuring and modelling the hydrological cycle at increasing temporal and spatial resolutions, scientific work in this field in mountain areas has however lacked behind. This study has taken a systems approach to the interaction between the hydrological cycle, climate change and agriculture in mountain catchments by contributing to four crucial topics. For the first topic knowledge on the spatial and temporal precipitation patterns across different land uses on the Tibetan plateau was enhanced. A time series of normalized difference vegetation index was manipulated using a Fast Fourier transformation. The manipulated signal proved to yield interesting information about the interaction between vegetation and precipitation and the absolute amounts of precipitation. The second topic focused on the assessment of the effects of climate change for the Brahmaputra basin. The historical trends in precipitation and temperature from 1900 onwards were analyzed. Regression analysis of historical precipitation showed an interesting significant relationship between monsoon precipitation and the temperature difference between the Tibetan plateau and the low-lying floodplains. Outputs of general circulation models were statistically and spatially downscaled and ensemble averages revealed accelerated increases in precipitation and temperature that seemed to be positively related to altitude. Multiple regression analysis revealed that the downstream summer discharge is subject to a steep increase, with will most likely result in an increase in flooding in the low lying plains of Bangladesh. For the third topic an innovative methodology was developed to calibrate the process based semi-distributed hydrological model SWAT. Instead of the traditional way of using stream flow gauge data, remotely sensed actual evapotranspiration was used for the calibration. Different sets of soil, land use, and meteorological parameters were optimised and the calibrated SWAT model was then used to evaluate water use and water productivity in the Upper-Bhima catchment in southern India. The final component adds a link between biophysical and economic modelling. The “payments for ecosystem service” concept to conserve water was implemented in an agricultural catchment on the Tibetan plateau, which has an important water supplying role for downstream areas. It was shown that by providing farmers with financial incentives they may shift from irrigated to rain-fed agriculture as long as the compensation is high enough. This integrated approach has shown fascinating results, has clearly added value and opened many new scientific avenues for the future to be explored

Quantifying the Water Tower of the Third Pole: State of the Art and Research Challenges

Mountains are the water towers of the world, particularly in Asia, where rivers all are fed from the Tibetan plateau and adjacent mountain ranges. In this area, referred to as the Third Pole, snow and glacial melt are important hydrologic processes, such that climate change is expected to seriously affect melt characteristics and related runoff. The Third Pole provides water resources to nearly two billion people in Asia. However, uncertainty about key hydrological processes at high altitudes generally precludes the assessment of the potential impact of climate change on runoff. First we review recent geodetic and direct mass balances measurement of glaciers and we compare observations to a regional scale analysis of corrected mass balance anomalies based on gravitation measurements derived from the GRACE satellite. We then assess the state of the art in modeling the impacts of climate change on the water resources of the Third Pole at different scales. Our analysis first shows the regional differentiation in the importance of snow and glacial melt water to total runoff and how this may potentially change in the future for five major Asian river basins. For this analysis we use a lumped degree day factor hydrological model that we force using remote sensing data on snow cover and precipitation and which is calibrated using observed discharge data . We then focus on a number of smaller benchmark glaciated catchments that cover all climatic zone of the Third Pole. Using a model that explicitly simulates glacier movement in combination with major hydrological processes at a high spatial resolution, we show the diversified response of glaciated catchment to climate change and test whether this response is related to the west-east gradient in climate. We conclude by formulating the future research challenges and major uncertainties related to hydrological modeling on the Third Pole

Quantifying the Water Tower of the Third Pole: State of the Art and Research Challenges

Mountains are the water towers of the world, particularly in Asia, where rivers all are fed from the Tibetan plateau and adjacent mountain ranges. In this area, referred to as the Third Pole, snow and glacial melt are important hydrologic processes, such that climate change is expected to seriously affect melt characteristics and related runoff. The Third Pole provides water resources to nearly two billion people in Asia. However, uncertainty about key hydrological processes at high altitudes generally precludes the assessment of the potential impact of climate change on runoff. First we review recent geodetic and direct mass balances measurement of glaciers and we compare observations to a regional scale analysis of corrected mass balance anomalies based on gravitation measurements derived from the GRACE satellite. We then assess the state of the art in modeling the impacts of climate change on the water resources of the Third Pole at different scales. Our analysis first shows the regional differentiation in the importance of snow and glacial melt water to total runoff and how this may potentially change in the future for five major Asian river basins. For this analysis we use a lumped degree day factor hydrological model that we force using remote sensing data on snow cover and precipitation and which is calibrated using observed discharge data . We then focus on a number of smaller benchmark glaciated catchments that cover all climatic zone of the Third Pole. Using a model that explicitly simulates glacier movement in combination with major hydrological processes at a high spatial resolution, we show the diversified response of glaciated catchment to climate change and test whether this response is related to the west-east gradient in climate. We conclude by formulating the future research challenges and major uncertainties related to hydrological modeling on the Third Pole