Non-Darcian groundwater flow in leaky aquifers

Abstract

A simplified method has been developed for solving leaky aquifer non-Darcian flow hydraulics. The principle of volumetric approach is combined with the confined-aquifer, time-dependent drawdown equation in an observation well. The groundwater flow in the leaky aquifer is assumed to obey a non-Darcian flow law of exponential type. The results are obtained in the form of type-curve expressions from which the necessary bundles of curves are drawn for a set of selective non-Darcian flow aquifer parameters. Although application of the methodology appears as rather limited but it provides a scientific contribution and extension of leaky aquifer theory towards nonlinear flow conditions. The methodology developed herein is applied to some actual field data from the eastern sedimentary basin in the Kingdom of Saudi Arabia.     

Quality control and homogeneity of Turkish precipitation data

Outlier trimming and homogeneity checking/correction were performed on the monthly precipitation time series of various lengths from 267 stations in Turkey. Outlier values are usually found during dry summer months, and are concentrated mostly over the southern parts of the country, where the dry period is most pronounced, implying natural extremes rather than wrong measurements. Homogeneity analysis was done using the Standard Normal Homogeneity Test, on an individual monthly basis, which led to many non‐testable series due to lack of reference stations, especially during summer months. Yet, remaining testable months were usually helpful for the assessment of homogenity, revealing a well distributed set of stations that proved to be homogeneous. There were still a number of stations which either could not be tested efficiently, or were classified as inhomogeneous. Lack of metadata is argued to be largely responsible for inefficient homogeneity testing. Copyright © 2008 John Wiley & Sons, Ltd.     

Aquifer heterogeneity determination through the slope method

In arid‐region wadis, groundwater storage lies within shallow Quaternary alluvium deposits, which are connected with the present‐day hydrological cycle and, therefore, are replenished due to occasional runoff and flash flood occurrences. The groundwater resources are precious in these environments; therefore, their potentiality must be assessed with care in the best manner. The aquifer potentiality is calculated after the storativity and transmissivity parameter estimations, which require rather long‐duration field tests with restrictive assumptions in the theoretical model developments, such as the homogeneity and isotropy. It is the main purpose of this paper to expose the fundamentals of the slope‐matching procedure (SMP) and its application for short‐duration field tests in arid‐region aquifers. In this manner, the subsurface hydrogeological behaviours of the bored land pieces at and around the well locations are prospected in a detailed and refined manner. It is shown that in many cases the classical techniques are appropriate, inconvenient and inapplicable with conclusive reliable results and conclusions. The application of the SMP is presented for some aquifer tests from the central western part of the Kingdom of Saudi Arabia. Copyright © 2007 John Wiley & Sons, Ltd.     

The H N method for Milne problem with polarization

The H _N method, employed for studies in neutron transport theory, is used to establish numerical results basic to the vector equation describing the transfer of polarized light in a Rayleigh scattering atmosphere with true absorption. The method has been applied to the classical Milne problem. The exit distribution is defined as a series in powers of the zenith observation angle. The numerical results are computed and compared with exact values obtained using the exit distribution in terms of the H-matrix. The numerical results are in good agreement with previously published findings.     

A new spatial prediction model and its application to wind records

Summary Contour maps of any meteorological variable cannot give radius or area of influences around the measurement station by considering the records at surrounding sites. The main purpose of this paper is to propose a trigonometric point cumulative semivariogram (TPCSV) concept for deciding on a spatial dependence function and then its use for regional prediction. The TPCSV provides a unique opportunity for the establishment of a regional objective prediction method whereby the radius of influence helps to predict wind velocity at any site by using the weighted averages. The spatial correlations and weightings are obtained through the TPCSV provided that the distance between two sites is known. If the slope of TPCSV is greater than 80° after some distance, then beyond this distance the regional correlation is considered as negligible. The implementation of the proposed methodology is presented for 68 wind velocity measurement stations in Turkey. The proposed method yields the least prediction error compared with other objective methodologies. It is seen that areas of influence at Central Anatolia are generally bigger than coastal areas of Turkey.     

Climate change in Turkey for the last half century

Climate change and its urban-induced bias in selected Turkish cities is studied with a quality controlled temperature and precipitation data of Turkish stations in the period of 1950–2004. These stations are classified into two groups according to their populations; S1, including rural and suburban stations and S2, including large urban stations. Moving average signals, 365-day, and their digital low pass filtered versions are produced to eliminate the short term fluctuations and examine the possible trends or anomalies in climate data. Furthermore, ‘relative difference’ signals are introduced and applied to temperature and precipitation series to observe the actual local changes in the climate data independent from large-scale effects. Mann–Kendall test statistics are calculated for maximum, minimum, mean temperature and precipitation series and plotted on maps to determine any spatial trend patterns. Signal analysis show a cool period extending from early 1960s till 1993, generally with the lowest temperature values on 1992–1993 owing to the eruption of Mount Pinatubo. A last decade significant warming trend is observed in both of the series, S1 and S2, leading to 2000–2002 temperatures to be recorded as maximums in record history. The variability of urban precipitation series is generally larger than the rural ones, suggesting that urban stations can experience more frequent and severe droughts and floods. Though not significant, an increase in the urban precipitation compared to the rural one is also found. Spatial analysis resulted in significant warming in southern and southeastern parts of the country. Particularly, minimum temperature series show significant warming in almost all of the regions indicating the effect of urbanization. Significant decreases of precipitation amounts in the western parts of Turkey, such as Aegean and Trachea regions, are found. On the other hand, some Turkish northern stations show increases in precipitation of which some are significant.