In West Africa, particularly in Côte d'Ivoire, the groundwater is contained in hard-rock aquifers and serves as main source of drinking water supplies to the population. To improve access, several studies were conducted in various parts of the country. Most of them use mapping of lineaments related to tectonic fractures to represent corridors of groundwater. In this article, chemistry of major ions was used to highlight quantitatively the axes of groundwater movement, and mixing between different aquifers in Sassandra watershed which is located in the Southwest of the Ivory Coast. The sampling campaigns were accomplished respectively during the dry and wet seasons in the department of Soubré (8 590 km2), located in Sassandra watershed, area where the effects of climate change are observed. The processing of satellite images (optical and active) has produced a map of major lineaments. Geographic positions and technical data of boreholes were integrated into a geographic information system (GIS) to identify point near major lineaments for groundwater sampling and chemical analysis. The waters were collected, and then analyzed by using atomic absorption spectrometer (AAS) and a Varian Vista ICP. The results indicate that groundwater samplings are primarily Ca-HCO3 type or NaK-HCO3 and NaK-SO4 types. Calcium and low pH were encountered in the highlands where infiltration of meteoric water occurs relatively quickly through preferential pathways. Chadha diagram has highlighted differences in the chemistry of groundwater between aquifers on one hand, and between systems of surface runoff and deep runoff on the other hand. Most groundwater seems to move relatively quickly. In addition, some groundwaters show a denitrification coupled with pyrite oxidation. These groundwaters have been longer circulating along opened fractures with gentle slopes. The observations and hydrochemical characterization, especially SO42-/Cl- ratio, permitted to identify axes of groundwater movements in the study area. However, the major lineaments which are similar to major fractures are not primarily responsible for the groundwater motions. Rather, there are small fractures and topography which control the flow of groundwater in the crystalline hard-rock. Also, the groundwater levels are not always guided by the major lineaments observed. Some small lineaments and topography control fairly the groundwater flow.
This paper describes an efficient methodology to link a comprehensive, distributed hydrologic model for California’s Central Valley to a crop production model. The resulting hydro-economic model allows for the dynamic calculation of crop acreages in response to water availability without simplifying groundwater or stream flow dynamics by the assumption of linearity or by resorting to a lumped-parameter approach. The linked hydro-economic model is used to simulate the effects of several drought scenarios on Central Valley’s agriculture and the groundwater resources. The drought scenarios are constructed as surface flow reductions that range from 30% to 70% for periods spanning from 10 to 60 years, with a 10-year spin-up and a 30-year recovery. The main finding is that Central Valley agriculture as a whole is resilient to severe drought. Despite an almost 40% cut in surface water deliveries for irrigation, the region suffers only a 10% cut in irrigated crop acres. However, after 60 critically dry years in a row, the linked model suggests that there will be regional impacts, including moderate impacts in the north Central Valley (Sacramento River Basin), locally severe in the middle of the Valley (San Joaquin River Basin), and severe in the south (Tulare Basin). The model runs indicate that extensive pumping during such a drought can cause permanent subsidence and may lead to new equilibrium groundwater levels.
The impact of climate changes on both sea level and the temporal and spatial distribution of runoff will affect water supply reliability and operations in California. To meet future urban water demands in the San Francisco Bay Area, local water managers can adapt by changing water supply portfolios and operations. An engineering economic model, CALVIN, which optimizes water supply operations and allocations, was used to explore the effects on water supply of a severely warmer drier climate and substantial sea level rise, and to identify economically promising long-term adaptations for San Francisco Bay Area water systems. This modeling suggests that Bay Area urban water demands can be largely met, even under severe forms of climate change, but at a cost. Costs are from purchasing water from agricultural users (with agricultural opportunity costs), expensive water recycling and desalination alternatives, and some increases in water scarcity (costs of water conservation). The modeling also demonstrates the importance of water transfer and intertie infrastructure to facilitate flexible water management among Bay Area water agencies. The intertie capacity developed by Bay Area agencies for emergencies, such as earthquakes, becomes even more valuable for responding to severe changes in climate.
Regions depending on winter snowpack for hydroelectricity generation may be adversely affected if spring temperatures increase. An inverse relationship between spring temperature and summer hydroelectricity generation is complicated by changing statistical properties of the variables involved. We use simple approaches to quantify, within broad limits, the effect of a change in spring temperature on hydroelectricity generation in subsequent months over a political entity as large and geographically diverse as the state of California, incorporating variables that are highly nonstationary in the mean and in covariances with each other. Looking at data from several simple perspectives provides insight and a physically realistic explanation of the observations. California’s high-elevation hydropower reservoirs mitigate effects of dry winters; precipitation is limiting and spring temperature has no detectable effect. Following wet winters, however, warm springs can lead to earlier snowmelt and increased spillage so that water storage is limited by high-elevation reservoir capacity; during cold springs the snowpack melts more slowly, allowing it to act as a water reservoir for a longer period of time so that water can be supplied as needed. Following winters with over 70 cm of precipitation, water supply is abundant and hydropower seems limited by generation capacity. Our results demonstrate limitations of California’s high-elevation hydropower system, especially if climate warms, and our findings should also aid in the development of more complex, physically based, hydrologic models to aid water managers.
Aims: Provide a review of key features and several applications of the family of Integrated Water Resources (IWR) models, as the key analytical tools used in evaluation of hydrologic conditions in support of the integrated regional water management (IRWM) programs in California. Methodology: IWR models are a family of models consisting of the Integrated Groundwater and Surface water Model (IGSM), the Integrated Water Flow Model (IWFM), and the IWFM Demand Calculator (IDC). IGSM is an integrated model that simulates the complete hydrologic cycle for a basin. The California Department of Water Resources (CADWR) has upgraded and enhanced the IGSM code and developed an enhanced version, called IWFM. In addition, CADWR extracted the land surface processes module of IWFM as an independent unit, called IDC, which can be used as a stand-alone model for estimating agricultural water demand, groundwater pumping, and deep percolation. The IWR models have been applied to many basins throughout California to evaluate hydrologic conditions, including evaluation of land and water use, surface water and groundwater flow, stream-aquifer interaction, reservoir operation, land subsidence, and regional water quality conditions. An ArcGIS-based Graphical User Interface provides a robust modeling platform for the IWR models. Results: The IWR models have had significant success in analysis of various types of water resources projects, such as integrated regional water management programs, groundwater management and conjunctive use operations, groundwater recharge investigations, water transfer programs, water quality, water demand and supply analysis, seawater intrusion, and climate change vulnerability and adaptation analysis. Conclusion: The IWR models are effective tools in analyzing the technical issues involved in integrated water management and planning in California. These IWR models are well suited for analysis of hydrologic conditions and alternative water management scenarios explored in various basin management and IRWM programs.
Objectives: The framework is designed to provide (i) for better understanding of factors contributing to urban resilience; and (ii) for comparison of climate change adaptation options. Methodology: Disasters occur at the intersection of hazards and vulnerabilities. As the climate changes, so do the patterns of climate hazards. Coastal megacities are faced with many challenges including (i) increased exposure to natural hazards such as hurricanes, typhoons, storm surges, sea-level rise and riverine flooding; (ii) pressures of increasing urbanization and population growth; and (iii) increased complexity of interacting subsystems. An original method for quantification of resilience is provided through spatial system dynamics simulation. The quantitative resilience framework combines economic, social, organizational, health and physical impacts of climate change caused natural disasters on coastal megacities. The developed measure defines resilience as a function of time and location in space. The framework is being implemented through the system dynamics model in an integrated computational environment. Conclusion: Data collection for the Coastal Megacity Resilience Simulator (CMRS) model input and discussions with local decision makers are actively being pursued concurrent with the model development for the primary case study coastal city of Vancouver, British Columbia, Canada. Future work includes developing policy driven adaptation scenarios, resilience model simulations, transfer of the resilience model to local community and capacity building.
Aims: Derivation of a closed-form expression for the duration of the daily insolation on surfaces of arbitrary uniform slope and aspect located anywhere on Earth, anytime of the year. Study Method: It is shown that the sunrise- and sunset-hour angles and the duration of daily insolation depend on the roots of the equation A cosΦ + B sinΦ + C = 0, in which Φ is the hour angle and A, B, and C are coefficients that involve the slope of the surface, the aspect of the sloping surface, the solar declination, and the latitude of a point of interest on the sloping surface. Results: The method to calculate the duration of daily insolation developed in this article is applicable to any sequence or combinations of days to obtain the total number of daylight hours over arbitrary periods. Solutions for double sunrise and double sunset situations are also derived in this paper. Conclusion: The closed-form equations developed in this paper can be used in conjunction with measurements of atmospheric transmissivity to calculate the direct solar insolation on a surface of arbitrary slope and aspect, yielding a powerful tool for agricultural, meteorologic, hydrologic, ecologic, and climatic studies and modeling.
The Haihe River Basin (HRB), located in northern China with a drainage area of 318,200 km2, is one of the most developed regions in China. With rapid population growth and economic development, the combined problems of water shortage and groundwater over-pumping significantly constrain the sustainable development in this area. In order to strengthen the unified management of groundwater and surface water, we developed hydrologic modeling of surface water and groundwater interaction by coupling SWAT (for surface water simulation) and MODFLOW (for groundwater simulation). The newly developed modeling framework reasonably captured the spatiotemporal variability of the hydrological processes of the surface water and groundwater in the study area. The modeling results showed a good agreement with the measurements of surface water and groundwater during 1996-2006. Results of model evaluation indicated that the developed model could be a promising tool in watershed management planning under the context of global climate change and the “South-North Water Transfer Project”. In the HRB, climate change has significant effects on surface hydrology as indicated by the predicted increases on actual evapotranspiration and precipitation during 2041-2050 relative to those during 1991-2000. Changes of groundwater storage were mainly contributed by water diversion which would reduce the requirement of water pumping from groundwater especially for domestic and industrial uses. By the middle of the 21st century, increased water supply by projected precipitation and water diversion would result in annual increases of 3.9~9.9 billion m3 for river discharge and 1.7~2.9 billion m3 for groundwater storage as annual averages.
In this paper, the Fuzzy Inference System is used for developing an operation model for the Zayandeh-Rud Dam and for planning downstream agricultural crop farms under different climatic conditions. The model consists of three stages: in the first, the storage volume of the reservoir in March is predicted based on both the inflow into the reservoir during the last three months and the Southern Oscillation Index (SOI) using the Adaptive Network-based Fuzzy Inference System (ANFIS). The second stage involves forecasting the annual release in the following year as the model output using both the reservoir storage in the last month of the previous year and the amount of Snow Water Equivalent (SWE) as FIS inputs. As the annual release from the reservoir has definitive effects on the cropping schedule, it may be regarded as a defining factor for climate conditions. The optimized planning of crops for the following year is developed based on the annual release from the dam as forecasted by the fuzzy rules in the third stage of the model. Comparison of observed data and FIS estimations shows that the method developed here is capable of making reasonable decisions about land use and improved crop patterns based on climate conditions. The results also show that the Mean Average Error (MAE) for calculating the water demand is lower than 4.0 percent and, further, that in the case of predicting the cropping area, this error is lower than 2.0 percent.
Global change is recognized as an additional potential stressor on already over-tapped groundwater systems. Mitigation of impacts due to global change requires planning for sustainable use of groundwater systems. Identifying and developing mitigation plans for sustainable use of groundwater resources require detailed knowledge of aquifer dynamics and temporal behavior for a higher level of certainty on which decisions can be made by a knowledgeable group of stakeholders. The principal hypothesis of this study was that a robust set of uranium (238U) and thorium (232Th) decay series data from multiple wellfields representing different confining and geochemical conditions would cluster in a meaningful manner using a fuzzy c-means technique for better understanding of aquifer dynamics for management purposes. Three conceptual models were represented by the wellfields: 1) a well-confined artesian aquifer; 2) an area receiving recharge via a confining layer window; and 3) a regional recharge zone where the aquifer sub-crops near the land surface. These conceptual models were defined as C1, C2, and C3 according to the respective definitions. Eleven samples from the three wellfields were analyzed for ten parameters consisting of 238U and 232Th decay series isotopes. The data clustered successfully into three cluster types providing discrimination of behavior within each wellfield. Clusters C2 and C3 were characterized by the higher values of 222Rn, 226Ra, 228Ra, and 224Ra. Whereas, C1 was characterized by a higher values of 228Th, which was mostly absent from C2 and C3. The data clustered as expected between the well-confined, window, and regional recharge conceptual models with insights into individual well behavior. The data offer a robust conceptualization of aquifer dynamics in the regional area that may benefit decision makers.
It is necessary predict the effect of aquifer stresses in surface water and wetlands and consider the mutual effects that are produced by the conjunctive use of surface water and groundwater. This was originally made with very simple idealized analytical methods. The next development was the application of finite differences or finite elements numerical models, but poses problems when the model has to be run many times to analyze different management alternatives. When aquifer behavior is linear, as in confined, semi-confined, or unconfined aquifers with not too large changes in its saturated thickness, it is possible to apply the superposition strategy through influence functions. That has simplified significantly modeling and improved the effectiveness of management models. However, for large models, long modeling periods and a large number of alternatives, it is needed to handle and store many influence functions and to consider and store all the previous stresses. In that case, the eigenvalue method can be a more appropriated option. This approach solves the spatially discretized flow equation explicitly and continuously in time, obtaining modal orthogonal components through very simple explicit state equations in function of time. To reduce the computational load, the simulation can be simplified with appropriate truncation using only dominant modes of the components at the expense of a small error. Efficient methods have been developed to get the modal components as well as to perform truncation with limited errors.
Aims: The hypothesis of this research is that it is possible to increase the drip irrigation lateral line length by using a larger spacing between emitters at the beginning of the lateral line and a smaller one after a certain distance, which would allow for a higher pressure variation along the lateral line under an acceptable value of distribution uniformity. Study Design: Non-pressure compensating drip hose is widely utilized for vegetables and orchards irrigation. Though there is a limitation, which is the lateral line length must be short to maintain uniformity due to head loss and slope, any procedure to increase the length is appropriate because it represents low initial cost of the irrigation system. Place and Duration of Study: This study was conducted at the College of Agricultural Sciences of Sao Paulo State University in Botucatu, SP, during the year 2011. Methodology: To evaluate this hypothesis, a nonlinear programming model (NLP) was developed. The input data were: diameter, roughness coefficient, pressure variation, emitter operational pressure, relationship between emitter discharge and pressure. The output data were: line length, discharge and length of the each section with different spacing between drippers, total discharge in the lateral line, multiple outlet adjustment coefficient, head losses, localized head loss, pressure variation, number of emitters, spacing between emitters, discharge in each emitter, and discharge per linear meter. Results: The mathematical model developed was compared with the lateral line length obtained with the algebraic solution generated by the Darcy-Weisbach equation. The NLP model showed the best results since it generated a greater gain in the lateral line length, maintaining the uniformity and the flow variation under acceptable standards. It also had lower flow variation. Conclusion: NLP model showed the best results when compared with the conventional procedure, generating gain in the lateral line length, keeping the uniformity and flow variation under acceptable standards.