Theoretical derivation of precipitation coverage probability from a set of heterogeneous point probabilities

Various meteorological studies require probabilistic modeling such as the flood, drought, and wet and dry spell occurrences. The most commonly employed approaches are based on the binomial probability distribution function (pdf), which is valid for homogeneous temporal and spatial probabilities. However, in practice, heterogeneous probabilities are very common, and in this case, the classical binomial pdf cannot be employed. This paper presents a rigorous probabilistic methodology for heterogeneous probabilities by considerations from the random field concept. The general form of the binomial pdf is derived and it is shown that for homogeneous probabilities it yields the classical binomial pdf exactly. The necessary analytical formulations are derived with the assumption that the meteorological occurrences at a set of sites or time periods (day, month, and year) are independent from each other. The probability statements derived in this paper are helpful in predicting the regional and temporal probable potential future meteorological occurrences. The application of the proposed methodology is presented for annual precipitation occurrences at six meteorology stations around Istanbul, Turkey.     

Strategic groundwater resources planning in arid regions

A strategic approach is presented for future groundwater reservoir planning in arid regions where the evaluation of groundwater resources is restricted by scarcity of rainfall, data paucity, restrictive and unrepresentative methodologies, weak economies, almost nonexisting management and optimization programs, frequent groundwater quality variables along short distances, etc. This paper explains the necessary steps in preparing an effective strategic planning program that is expected to provide all the necessary data for identifying alternative solution scenarios especially in arid regions. It is shown on the basis of available scarce data that the risk model of these factors appears as the logarithmic normal probability distribution. The basic decision variables in groundwater storage and recharge planning are furnished with application to Wadi Fatimah in the western central part of the Kingdom of Saudi Arabia along the Red Sea coast. The approach given in this paper provides a basic example for future groundwater reservoir strategic use and management studies in the Kingdom in particular and in any part of the arid regions of the world, in general.     

Rock Quality Designation Model Formulation and Simulation for Correlated Fracture Intact Lengths

An important factor in the rock quality assessment analysis from discontinuity measurements along a scanline is the correlation of intact lengths. The autorun model and first order autorun coefficient are proposed as a method for objectively quantifying intact length correlation structure and discontinuity occurrences along any scanline. Necessary definitions for the methodology are presented on a quantitative basis such as the alternative intact length percentages and experimental autorun coefficient. An expression is proposed for the number of discontinuity occurrences along a scanline depending on the scanline length, alternate intact length percentages, and the autorun coefficient. Monte Carlo simulation technique is used with a suitable autorun model to verify this expression. A mathematical expression is derived for the expected Rock Quality Designation (RQD) value by taking into account the correlation of the intact lengths. Additional simulations show the validity of the new RQD expression. With the methodology proposed much less engineering experience and judgment are required in estimating the RQD value from scanline measurements. The application of the methodology has been presented for some field data.     

Dimensionless straight line fitting method for hydrogeological parameter determination

Aquifers may have alluvium deposits, weathered layers, fractured zones, and karstic formations separately or in mixture forms. Such geological configurations do not allow classical aquifer test applicability, due to a set of underlying assumptions that are not usually valid in nature. In practice, the Jacob straight line method is the most commonly used approach for aquifer parameter determinations. Constant transmissivity and storativity estimations depend on large time-drawdown plots on semilogarithmic paper as a straight line. A common mistake is that the appearance of a general trend as a straight line on semilogarithmic paper is taken as guaranteed for the application of Jacob method. Since Jacob straight line is the large time extension of Theis type curve, there is only one straight line on the semilogarithmic paper that can represent Jacob method, which is based on the assumption that the aquifer is porous and homogeneous. In such a case, the Jacob method slope should equal to 2.3, which shows its validity. Otherwise, a modification of Jacob method is suggested in this paper. The basis of the methodology is a dimensionless type straight line approach for the aquifer parameter assessment. Its application is presented for aquifer test data from Oude Korendjik porous medium aquifer data. The application results indicate that the classical Jacob straight line method might not be valid without a preliminary check. The dimensionless reevaluation of existing data helps to check the validity. The necessary formulations for the modification of the classical straight line method are derived, which reduce to classical Jacob method for a specific set of parameters.     

Rock quality designation-fracture intensity index method for geomechanical classification

Rock quality designation (RQD) is a simple and effective way of rock mass classification from surface scanlines or preferably borehole measurements. A major drawback in its classical use is that only one representative RQD value is obtained from the field measurements per core run. However, it is shown in this paper that the field measurements along a scanline provide detailed information about the rock quality and the fracture intensity (FI) for a given number of joints. In order to be able to extract the complete information concealed within the field data, the RQD-fracture index diagram concept is proposed and applied to actual field scanline measurements from England. The basis of the suggested procedure is to obtain a series of all possible RQD and FI values from given intact length measurements. This procedure provides additional information as to the local zones of heterogeneities within the rock mass and a new way of rock classification on the basis of the combined effects of RQD and FI. It is also possible to calculate percentages of different rock qualities within the same rock mass.     

Global warming threat on water resources and environment: a review

Global warming, greenhouse effect, and the climate change problems are long-term anthropogenic consequences that are expected to threaten water related demand and supply patterns in the near future. These problems may be identified linguistically on a logical basis to take the necessary precautions, and implement mitigation strategies after vulnerability possibilities are assessed using fuzzy logic. Climate change effects are the focus of many scientific, engineering, economic, social, cultural, and global nuisances, and these effects awaits cost-effective remedial solutions. Extreme events such as floods and droughts and modified groundwater recharge may be influenced by climate change.     

River suspended sediment modelling using a fuzzy logic approach

Correct estimation of sediment volume carried by a river is very important for many water resources projects. Conventional sediment rating curves, however, are not able to provide sufficiently accurate results. In this paper, a fuzzy logic approach is proposed to estimate suspended sediment concentration from streamflow. This study provides forecasting benchmarks for sediment concentration prediction in the form of a numerical and graphical comparison between fuzzy and rating‐curve models. Benchmarking was based on a 5‐year period of continuous streamflow and sediment concentration data of Quebrada Blanca Station operated by the United States Geological Survey. The benchmark results showed that the fuzzy model was able to produce much better results than rating‐curve models. The fuzzy model proposed in the study is site specific and does not simulate the hysteresis effects. Copyright © 2006 John Wiley & Sons, Ltd.     

Flash flood inundation map preparation for wadis in arid regions

Flood inundation maps are dependent on the topographic and geomorphologic features of a wadi (drainage basin) in arid regions, which are most susceptible for potential flash flood occurrences, such as in the southwestern part of the Kingdom of Saudi Arabia. It is not possible to control the potential flood hazards by using only technological instruments that forewarn the occurrences or imminence. Additionally, it would be better to prepare flood risk maps so as to delineate the risky areas to educate the administrators and local settlers. The availability of these maps is the key requirement for any urban development that entails land use allocation, identification of dam, tunnel, highway, bridge sites, and infrastructure locations for sustainable future. This paper suggests the necessary steps in flood inundation map preparation after determining the possible flood discharge. For this purpose, a set of critical cross-sections along the possible flood plain are taken in the field with surveying methods and measurements. The calculation of the average flow velocity in each section is calculated according to the cross-section geometric, hydraulic, and material properties. Synthetic rating curves (SRC) are prepared for each cross section, which are very useful especially in arid and semi-arid regions where there are no perennial surface water flows for natural rating curve measurements. All the SRCs appear in the form of power function which relates the flow depth to discharge in a given cross section. It is then possible to calculate the flood depth in the cross section through its SRC. Depending on the cross-section shape, the flood width can be calculated. The connection of a series of widths on a scaled topographic map delineates the flood inundation area. If digital elevation map (DEM) is available, then the SRCs can be integrated with these maps and the flood inundation delineation can be achieved automatically. Since DEMs are not available, the topographic maps are used for this purpose in order to delineate flood inundation areas within wadis Hali and Yiba from the southwestern Kingdom of Saudi Arabia.     

Ground water quality assessment using multi-rectangular diagrams

A new graphical technique is proposed here for classifying chemical analyses of ground water. In this technique, a diagram is constructed using rectangular coordinates. The new diagram, called a multi-rectangular diagram (MRD), uses adjacent multi-rectangles in which each rectangle represents a specific ground water type. This new diagram has the capability to accommodate a large number of data sets. MRDs have been used to classify chemical analyses of ground water in the Chaj Doab area of Pakistan to illustrate this new approach. Using this graphical method, the differentiated ground water types are calcium bicarbonate, magnesium bicarbonate, sodium bicarbonate, and sodium sulfate. Sodium bicarbonate emerges as the most abundant ground water type. MRDs also offer a visual display of the Chebotarev sequence of ground water quality evolution.     

Modified rock mass classification system by continuous rating

It is not the purpose of this paper to propose a new rock mass classification system but rather to improve the existing ones by incorporating some simple quantitative interpretations. The geomechanics classification system of naturally fractured rock masses is modified to decrease personal judgement involved in its calculation. Instead of six parameters in the classical rock mass rating (RMR) system, only five basic parameters are considered in the proposed system, which are namely, rock quality designation (RQD) value with the underlying frequency distribution function of intact lengths; uniaxial or point load strength of intact rock material; conditions of the most unfavorable joints; groundwater condition; and joint orientation. Classical lump-rating system is replaced by continuous grading system which leaves no ambiguity for an inexperienced engineer in allocating grades based on quantitative field or laboratory measurements. Finally, necessary charts are presented for obtaining straightforward design values concerning average stand-up time and corresponding unsupported span of excavations in fractured rock mass; cohesion as well as friction angle of the rock mass. The continuous RMR system is very convenient for calculators or in writing computer software. The proposed methodology reduces the scale of subjectivity and leads to a unique rock mass design value.