A.A.M.F.R. Smit’s research while affiliated with Wageningen University & Research and other places

A better use of land and water resources will be necessary to meet the increasing demand for food in the Nile basin. Using a hydro-economic model along the storyline of three future political cooperation scenarios, we show that the future of food production in the Basin lies not in the expansion of intensively irrigated areas and the disputed reallocation of water, but in utilizing the vast forgotten potential of rainfed agriculture in the upstream interior, with supplemental irrigation where needed. Our results indicate that rainfed agriculture can cover more than 75% of the needed increase in food production by the year 2025. Many of the most suitable regions for rainfed agriculture in the Nile basin, however, have been destabilized by recent war and civil unrest. Stabilizing those regions and strengthening intra-basin cooperation via food trade seem to be better strategies than unilateral expansion of upstream irrigation, as the latter will reduce hydropower generation and relocate, rather than increase, food production.

De KRW-Verkenner 2.0 is een door Deltares, Alterra en PBL gezamenlijk ontwikkeld model-instrument dat beoogt om de waterbeheerders ondersteuning te bieden bij het opstellen van hun stroomgebied beheersplannen door het verkennen van de effecten van maatregelen (of maatregelpakketten) op de resulterende waterkwaliteit en op de ecologische doelstellingen op het schaalniveau van een waterlichaam. Toepassingen van de Verkenner zijn niet gebonden aan een specifieke ruimtelijke schaal. De eerste toepassing van deze nieuwe versie is in opdracht opgezet als landelijke modeltoepassing met als hoofddoel om de berekende nutriëntenconcentraties aan bemeten oppervlaktewateren te kunnen valideren. Alle datastromen en bewerkingen zijn vastgelegd in een R-script.

Aardappel, een zouttolerant voedselgewas, is als testgewas gebruikt om te onderzoeken of productie met beregening met brak- of zoutwater mogelijk is en de invloed op de opbrengst.

De KRW-verkenner, KRW-ECHO zijn voorbeelden van modellen die worden ingezet voor scenariostudies om effecten van bestaand en voorgenomen beleid op de stikstof- en fosforbelasting van het oppervlaktewater in beeld te brengen. Het is gewenst om de diffuse uit- en afspoeling bij regionale toepassingen van de KRW-verkenner en KRW-ECHO te verbeteren.

Parameters of the distributed irrigation water management model FRAME are determined by an inverse method using evapotranspiration (ET) rates estimated from the SEBAL remote sensing procedure and in situ measurement of groundwater heads. The model simulates canal and on-farm water management as well as regional groundwater flow. The calibration is achieved in two phases. The data on ET were introduced with the primary intent of improving predictions of ET through better estimated soil hydraulic parameters. During the first phase, soil hydraulic parameters sensitive to ET were optimized. As per the canal running schedule in the study area, the daily values of ET data were synthesized into 16 time periods with 15 periods each of 24 days and one period of 5 days. Use of cumulative (annual basis) ET data results in better estimates of soil hydraulic parameters as compared to temporal (24-day period basis) ET data due to possible errors in other input data. During the second phase of calibration, aquifer drainable porosity and maximum allowable groundwater extraction were optimized against groundwater heads for five years. The calibration was very successful in about 70% of the study area with a coefficient of correlation between simulated and observed groundwater levels of more than 80%. Subsequently the model is validated against groundwater heads for nine years. Copyright © 2009 John Wiley & Sons, Ltd.

Deze rapportage richt zich op het bemalingsgebied Quarles van Ufford. Om zicht te krijgen op de nutriëntenhuishouding in het gebied is er vanaf 2004 aanvullend op het reguliere meetnet van het waterschap in het oppervlaktewater gemeten. Voor de interpretatie van deze meetgegeven en het leggen van relaties om de bronnen en transportroutes van nutriënten in beeld te brengen waren modellen en aanvullende metingen noodzakelijk. In dit synthese-rapport worden de bronnen, routes en de sturingsmogelijkheden om de nutriëntenkwaliteit in het oppervlaktewater van Quarles van Ufford te verbeteren beschreven.

Soil water flow modelling approaches as used in four selected on-farm water management models, namely CROPWAT, FAIDS, CERES and SWAP, are compared through numerical experiments. The soil water simulation approaches used in the first three models are reformulated to incorporate an evapotranspiration process similar to that used in SWAP. Computations are carried out for three soil types, representing sandy loam, loam and sandy clay loam. The reformulated models are calibrated against simulation results obtained with SWAP. All the modelling approaches predict nearly equal estimates of cumulative actual evapotranspiration for a wheat crop. When compared with SWAP simulation results, the CERES type approach outperformed the other two approaches in respect of estimated cumulative deep percolation losses. A new criterion is proposed to interpret simulation results under deep water table conditions to suggest appropriate depth of water application. The resulting recommendations for irrigation planning suggest that any of the modelling approaches may be used to suggest practical irrigation considered in the present study. Copyright © 2008 John Wiley & Sons, Ltd.