A Systems Approach to Design of Agricultural Drainage Systems in Egypt

Agricultural drainage systems provide the principal means of coping with waterlogging and salinization of soils, two of the major environmental problems of agriculture. To illustrate the enormity of the problems caused by salinization, one need only note that the total soil loss in the world due to secondary salinization is larger than the amount of soil presently irrigated worldwide. Dr. Strzepek's paper is written from a perspective unusual at IIASA. Generally, the type of decision which concerns IIASA scientists is one of feasibility -- whether a specific project should be developed and what the principle features of such a project would be. In contrast, Dr. Strzepek's approach is to discuss the ways in which the techniques of systems analysis can be used to solve universal problems of engineering design. This methodological point of view is thus of interest not only to the task "Environmental Problems of Agriculture, "but also to the entire institute and decisionmakers in general. The background work for this paper was initiated at the Massachusetts Institute of Technology, but the paper was written at IIASA

Analysis of Tile Drainage Design Policies in Egypt

Recent field studies have shown that in some cases tile drains have been ineffective in increasing crop production. This paper examines the effect that the policies of 40 meter minimum spacing and aggregating large areas under a single drain design may have upon the effectiveness of tile drains. An approach that synthesizes crop yield response, the physics of drainage and economics is used to determine the possible cost of these two policies. A case study from the Nile Delta is examined. The paper shows that these policies can have a great effect upon the efficiency of tile drain performance under certain conditions

MITSIM-2: A Simulation Model for Planning and Operational Analysis of River Basin Systems

Mathematical simulation models have become a common tool for the analysis of water resources problems . The models fall in two categories, those for studying long range planning of water resources development and those for the analysis of detailed operation of water resource systems. The planning models tend to be of a longer time step usually on the order of one month, while the operational models may need a time steps of days and in some cases hours. This paper presents a model that incorporates features of both planning models and operational models. MITSIM-1, a river basin simulation model for long range planning was modified to account for daily operational rules and complex institutional constraints within a basin. A new model ,MITSIM-2 , was developed that provides quasi-daily operational rules for reservoirs and irrigation requirements, while retaining the features necessary for efficient long range planning of basin development . MITSIM-2 is applied to the regional water supply system of South Western Skane to demonstrated its applicability to incorporate planning and operational analysis successfully in one model

Potential Evapotranspiration Methods and their Impact on the Assessment of River Basin Runoff Under Climate Change

The current trend in increased amounts of green house gases in the atmosphere will likely affect both precipitation and evapotranspiration, which will in turn affect the runoff response of river basins. These impacts on river basin discharge are discussed in the context of changes in evapotranspiration estimates which are found by coupling a monthly water balance model to account for changes in soil moisture and micrometerological and empirical estimates of potential evapotranspiration. The purpose is to assess the importance of the varying methods for estimating potential evapotranspiration on climate impact assessments of river basin discharge. Four river basins of different size and hydro-climatic variability were selected as case studies

Examining the Impacts of Land-Use Change on Hydrologic Resources

The research community over the past several years has put a great effort into studying the potential impacts of a changing climate. But the issues that face the world today encompass greater change than just that of climate. For instance, there are changes due to population dynamics (such as migration), economics, and the way that land is used. Water resources are affected specifically by changes in climate and land use. A water balance developed for the purpose of examining climate change was extended to allow analysis of impacts from land-use change. In addition, it was modified so that a watershed could be modeled by multiple smaller units within the basin. Two methodologies were applied to break the basin into smaller parts: first, hydrologic boundaries of major tributaries were used, and second, a delineation based on five classes of land-use type, which included tundra, forest, rangeland, agriculture, and urban land, was created. The model originally had three parameters which were calibrated statistically. A goal of this project was to take a step towards making these parameters physically-based in the watershed, thereby avoiding the need for statistical calibration which might allow parameters to mask interconnections in the hydrologic process. The parameter which represents maximum soil moisture capacity was therefore set based on land-use type. The South Platte Basin upstream of the town of Masters, Colorado was chosen as a case study basin. The study included eight sub-basins delineated by hydrologic boundaries and the five land classes mentioned previously. A climate change sensitivity analysis was performed and a hypothetical land-use scenario was analyzed. This hypothetical scenario increased the percentage of urban land and removed all agriculture. In addition, some rangeland was converted to forested land. These tests were examined individually and in a combined scenario. Results found that the land-use scenario estimated greater runoff and acted to mitigate negative effects and enhance positive impacts of climate change. The magnitude of the impact of land-use change was found to be of the same order as that of climate change, and it therefore further warrants further research into possible effects of such changes. The study clearly demonstrated the sensitivity of model results to inclusion of land-use change, and the need for further development of the hydrological model for the Yellow River basin in North China, a water-critical region of the LUC project study area

Integrated Water Demand/Supply Management in Southwestern Skane: A Preliminary Analysis

The water management system in South-Western Skane features different water supply sources (surface and groundwater), municipal water demand zones, and several agricultural water users. In the future the Bolmen Lake scheme will be made operational. The major question now is what are the advantages and disadvantages of integrating all sub-regional solutions into a regional water resources system (particularly in terms of increased reliability). River Basins are the main feature of the sub-regional water resource systems in South Western Skane. A simulation model, MITSIM-2, was developed to analyze the hydrologic performance of these systems. Using this model and water use projections based upon projections of the future demo-economic structure of South Western Skane, a preliminary analysis of a regionally integrated water supply system was performed. This analysis examined the ability of the regionally integrated system to satisfy the water requirements of South Western Skane under different development scenarios

CHARM: A Hydrologic Model for Land Use and Climate Change Studies in China

China is a country, which is rapidly changing and developing. The population is enormous and still increasing and the economy is growing at a rate that is one of the world's fastest. These factors are placing substantial stress on China's natural resources. Already, the best agricultural land is used and cities are expanding on top of some of this fertile land. Cities are growing so fast that improving and increasing electric and water infrastructure cannot keep up with demand. Much of Northern China is already in a situation of severe water stress. In order to understand how the resource stress will affect China's development, knowledge of the currently available resource in any area is necessary. Furthermore, possible changes in the resource availability in the future must be understood. These changes could be natural or anthropogenic ranging from climate change to changing land from pasture to irrigated farmland. If good data is available, the current resource availability is already known for all areas and a model can be used to investigate the impacts of any changes to the system. However, if good data is not available, a model must be used to gain both the current state and the impacts of changes. The latter is the method employed here to assess China's water availability. In this paper, a hydrologic model is developed to assess China's water availability. CHARM, for Climate and Human Activities sensitive Runoff Model, is developed to provide the runoff produced from rainfall throughout China on a 5 km x 5 km grid-cell resolution. The model is calibrated to average annual watershed runoff values. CHARM can then not only supply currently available surface water runoff for entire regions, but can supply runoff and runoff variability inter-annually and intra-annually for any area desired. Furthermore, it can be used to assess the impacts of land use and climate change on water resources. Here, the methodology of CHARM is developed and validated on two watersheds in the Yellow River Basin in China. It is then used to assess the current water resource supply in China. Finally, the strengths and weaknesses in the model and the modeling approach are discussed to assist the modeler in interpreting the results

Comparison of Models for Climate Change Assessment of River Basin Runoff

Two lumped-integral conceptual models, a non-parametric regression model and two annual "screening" models are used to compare the impact of climate variability on 5 basins at varying spatial scale and climactic characteristics around the world. Where data were available, different time steps were used to address the influence of the temporal scale on climate impact assessment of river runoff. The purpose of this exercise is to gain insight into the general applicability of these models and assess the impact of spatial and temporal scale on model results derived from changes in two key climate variables: precipitation and temperature. For two of the basins, the East River in Colorado USA and the Mulberry River in Arkansas USA, a comparison is made between these models and results taken from past research on basins using distributed integral models on a 6 hour time step. An additional objective of this study was the selection of a robust model that can be used to assess regional vulnerability of water resources to climate change where data availability is limited