Abstract. The hydrological response of Swiss river basins to the 2003 European summer heatwave was evaluated by a combined analysis of historical discharge records and specific applications of distributed hydrological modeling. In the summer of 2003, the discharge from headwater streams of the Swiss Central Plateau was only 40%-60% of the longterm average. For alpine basins runoff was about 60%-80% of the average. Glacierized basins showed the opposite behavior. According to the degree of glacierization, the average summer runoff was close or even above average. The hydrological model PREVAH was applied for the period . Even if the model was not calibrated for such extreme meteorological conditions, it was well able to simulate the hydrological responses of three basins. The aridity index φ describes feedbacks between hydrological and meteorological anomalies, and was adopted as an indicator of hydrological drought. The anomalies of φ and temperature in the summer of 2003 exceeded the 1982-2005 mean by more than 2 standard deviations. Catchments without glaciers showed negative correlations between φ and discharge R. In basins with about 15% glacierization, φ and R were not correlated. River basins with higher glacier percentages showed a positive correlation between φ and R. Icemelt was positively correlated with φ and reduced the variability of discharge with larger amounts of meltwater. Runoff generation from the non-glaciated sub-areas was limited by high evapotranspiration and reduced precipitation. The 2003 summer heatwave could be a precursor to similar events in the near future. Hydrological models and further data analysis will allow the identification of the most sensitive regions where heatwaves may become a recurrent natural hazard with large environmental, social and economical impacts.
Paddy field storage of rainfall by bunds is like a rainwater cistern system during the rainy season. Deepwater management practice in paddy fields might be good for rice production and water storage capacity at the same time. The study was conducted in an experiment testing two water management treatments with six rice variety treatments using two lysimeter experiments.The results revealed that deepwater management significantly affected rice production. On the other hand, deepwater management increased the effective rainfall (70 mm) and percolation (225 mm). The runoff coefficient under deepwater management decreased from 0.67 to 0.53. It was reasonable to conclude that the deepwater management provided more water storage capacity during the growing season. Finally, water productivity results point out that even though the volume of input water under deepwater management had increased, deepwater management still can generate higher water productivity.It looks as if it is pointless to save water during the rainy season. On the contrary, if excess water is available in rivers, it should be delivered in timely fashion to the wetland rice fields to increase effective rainfall and the excess saved by maintaining adequate percolation to replenish groundwater, without having to follow strict water conservation measures. Copyright # 2007 John Wiley & Sons, Ltd. RÉ SUMÉ Le stockage des précipitations dans les rizières au moyen de diguettes est analogue à la récupération de l'eau de pluie par citerne. La pratique de la gestion de plan d'eau dans les rizières pourrait être une bonne chose à la fois pour la production de riz et la capacité de stockage de l'eau. L'étude porte sur une expérience combinant deux types de gestion de l'eau, six variétés de riz et deux sortes de lysimètre.Les résultats montrent que la gestion de plan d'eau a affecté de manière significative la production de riz. Par ailleurs elle a augmenté les précipitations efficaces (70 millimètres) et la percolation (225 millimètres). Le coefficient d'écoulement a diminué de 0,67 à 0,53. Il était donc raisonnable de conclure que la gestion de plan d'eau a augmenté la capacité de stockage de l'eau pendant la saison de croissance. Et finalement, les résultats de productivité de l'eau montrent que, en dépit de l'augmentation du volume d'eau entré dans la rizière grâce à la gestion de plan d'eau, cette dernière permet une productivité de l'eau plus élevée.
Abstract:The potential benefits of increased application of water to paddy fields in Taiwan are investigated in this paper. A conceptual model is used to represent the hydrological system of the paddy field. A technique is presented to estimate the parameters of the model. Field experiments also are performed for parameter estimation and model verification. The simulated results are in good agreement with the observed during model verification. With parameters estimated from the field data, the model is used to simulate the effects of applying water beyond current practice. The simulation results show that the downward percolation increases when the irrigation water increases. However, the percolation reaches a capacity rate no matter how large the amount of water applied. This phenomenon results from the existence of a hard layer below the paddy field. The effects of raising the height of levees around paddy fields are also studied.
In this paper a water reuse system in wetland paddy was simulated to supply water for industry. A two-tank model was employed to represent the return flow of the wetland paddy. Historical data were used for parameter estimation and model verification. The simulation results show that the return flow from wetland paddy has potential benefit for water reuse. Under a series of water management strategies, about 87% of the total volume of return flow can supplement industrial water needs which decreases local water needs by about 22.4%. The strategies include increasing the volume of return flow through deepwater management practices, stabilizing the reuse of return flow in the purification unit through the regulated large-capacity pond downstream, and harmonizing the supply-anddemand gap through a suitable cultivated paddy scale of the crop rotation pattern. Apart from meeting water needs at peak demand periods, the reuse of return flow is a quick-response water supply solution. Accompanied by the series of water management strategies, water reliability and crop security can be achieved at the same time.
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