Trends in hydrological and climatic variables affected by four variations of the Mann-Kendall approach in Urmia Lake basin,Iran

ABSTRACT

The trends in hydrological and climatic time series data of Urmia Lake basin in Iran were examined using the four different versions of the Mann-Kendall (MK) approach: (i) the original MK test; (ii) the MK test considering the effect of lag-1 autocorrelation; (iii) the MK test considering the effect of all autocorrelation or sample size; and (iv) the MK test considering the Hurst coefficient. Identification of hydrological and climatic data trends was carried out at monthly and annual time scales for 25 temperature, 35 precipitation and 35 streamflow gauging stations selected from the Urmia Lake basin. Mann-Kendall and Pearson tests were also applied to explore the relationships between temperature, precipitation and streamflow trends. The results show statistically significant upward and downward trends in the annual and monthly hydrological and climatic variables. The upward trends in temperature, unlike streamflow, are much more pronounced than the downward trends, but for precipitation the behaviour of trend is different on monthly and annual time scales. Furthermore, the trend results were affected by the different approaches. Specifically, the number of stations showing trends in hydrological and climatic variables decreased significantly (up to 50%) when the fourth test was considered instead of the first and the absolute value of the Z statistic for most of the time series was reduced. The results of correlations between streamflow and climatic variables showed that the streamflow in Urmia Lake basin is more sensitive to changes in temperature than those of precipitation. The observed decreases in streamflow and increases in temperature in the Urmia Lake basin in recent decades may thus have serious implications for water resources management under the warming climate with the expected population growth and increased freshwater consumption in this region.

Editor Z. W. Kundzewicz; Associate editor Q. Zhang     

A numerical study on the basin edge effect on soil amplification

In this paper a numerical study on the effects of the basin edge on the dynamic behavior of the model basins are investigated. For this purpose a range of bedrock inclinations at the valley sides from slighter $10^{\circ }$ and $20^{\circ }$ to steeper $30^{\circ }$ and $40^{\circ }$ are selected. A numerical study using nonlinear code which utilizes appropriate static and dynamic boundary conditions, and includes hysteresis damping formulation based on user defined degradation curves is conducted utilizing two sandy and clayey materials. Using several different real earthquake motions provide opportunity for the assessment of the site response to the variation of the motion intensity. The analyses results are presented in the form of the acceleration and spectral acceleration amplification curves. Also, by conducting 1D analyses along the valley the aggravation curve for every case are evaluated and discussed. It was seen that variation of the bedrock inclination not only affects the peaks of the spectral amplification curves, but also the position of the maximums of the curves on the valley surface are changed. Also, the frequency domain results show that different parts of the valleys are sensitive to different periods. While the lateral parts are sensitive to lower periods, the maximum amplification of the inner parts takes place at higher periods. Based on results the 2D behavior not only is dominant at the latreal parts of the valley, but also affects the behavior of the inner parts. Also, the use of the 1D analyes for the estimation of the 2D behavior remains insufficient. Finally, the results of this research show the important effect of the motion intensity on the 2D behavior of the valley specially on the increase of the resonance period at higher period.     

Analysis of karst spring recession curves,west of Iran

The recession hydrographs of karst springs provide important information about aquifer characteristics such as storage properties and drainage potential, karstification degree, and other hydrological features. The Faresban, Famaasb, Gonbad-e-Kabood, and Gian springs are the important karst springs which drain main karst aquifers in west of Iran. In this study, we evaluate hydrological characteristics of these four karst springs using different analytic equations. Almost, all the recession curves were well fitted by a function that consists of three main exponential terms. The initial portion of the recession curve represents the fast drainage of large fractures and conduits, ending with the slowly decreasing curve, where the drainage of rock matrix and small fissures or baseflow is dominant. The Gian spring has the largest storage volume but the lowest drained water (7%). Using Mangin’s equation, it is apparent that the baseflow supplies over 85% of the total drained water to the Gian spring, while a small quantity of total outflow is made up of quickflow periods. Of the water available to the Famaasb, Faresban, and Gonbad-e-Kabood springs, 85, 80, and 70% are drained during period of baseflow, respectively, whereas the quickflow periods have minor importance in some springs. Based on the Coutagne’s equation results, it can be concluded that the catchment of the Famaasb and Gonbad-e-Kabood springs have a karstified saturation zone with drainage channels that provide a rapid discharge with little storage capacity. At Gian catchment area, the initial discharge is not as rapid as karstification but is fairly homogeneous throughout the aquifer.     

Geodynamic evolution of the Sabzevar zone,northern central Iranian micro-continent

Mineralogy and Petrology - The Northern Central Iranian Micro-continent (CIM) represents Neotethys-related oceanic crust remnants, emplaced due to convergence between CIM and Eurasia plates during...     

Trend analysis of rainfall pattern over the Central India during 1901–2010

In the present study, trends of rainfall of the Central India were evaluated in monthly, seasonal, and annual time scales using the Revised Mann-Kendall (RMK) test, Sen’s slope estimator, and innovative trend method (ITM). For this purpose, the monthly rainfall data for 20 stations in Madhya Pradesh (MP) and Chhattisgarh (CG) states in Central India during 1901–2010 was used. The Sen’s slope estimator was utilized for calculating the slope of rainfall trend line. Based on the obtained results of RMK test, there is no significant trend in the stations for the January and October months. The results also showed that for MP, two out of 15 considered stations indicate significant annual trend, while the CG has four out of five stations with significant trend. The results of applying ITM test indicated that most of the stations have decreasing trends in annual (16 stations), summer (16 stations), and monsoon (11 stations) seasons, while the winter (12 stations) and post monsoon (11 stations) seasons generally show increasing trend. Unlike the RMK, the ITM shows significant increasing trend in rainfall of November and December months. The finding of current study can be used for irrigation and water resource management purpose over the Central India.     

Determination of the optimum sealing method for Azad pumped storage dam considering seepage analysis

Seepage analysis of the upper reservoir of the Kurdistan Azad pumped storage dam with a volume of 3.8E+5 m³ is a key step for selection of the optimized sealing method. More than 60% of the Lugeon test results show very permeable behavior for the pit and abutments of the reservoir. In this study, regarding the permeability value of the reservoir abutments and pit obtained by means of Lugeon tests, seepage rate was computed using various analytical and numerical methods. Reservoir total seepage discharge was computed in steady-state regime by means of analytical and numerical methods (SEEP/W finite element software) as 1.14E+05 and 1.15E+05 m³/day, respectively. Distinct element method (UDEC software) showed variable behavior for the seepage flow. In the reservoir initial impounding stages, the amount of seepage was very high (1.70E+06 m³/day). Then, the seepage rate decreased gradually and reached to a constant value (1.12E+05 m³/day). For the reservoir 3D modeling, Seep3D commercial software was used and has shown water seepage discharge of about 1.18E+05 m³/day, means 3% of total reservoir volume. Based on the above-mentioned results and regarding behavior of seepage in the initial impounding stages, sealing element is necessary to prevent from seepage phenomenon. Clay blanket, concrete lining, asphaltic concrete, and geosynthetic are the proposed methods in a large water reservoir. After a feasibility study on various sealing methods, geomembrane was suggested as the best sealing method with the reasonable implementation cost.     

Review of the Cambrian volcanic activity in Morocco: geochemical fingerprints and geotectonic implications for the rifting of West Gondwana

International Journal of Earth Sciences - Volcanic activities related to the opening of a Cambrian rift in Morocco were widespread from the Fortunian to the Cambrian Epoch 3. Numerous data are...     

Estimating liquefaction-induced settlement of shallow foundations by numerical approach

Occurrence of liquefaction in saturated sand deposits underlying foundation of structure can cause a wide range of structural damages starting from minor settlement, and ending to general failure due to loss of bearing capacity. If the bearing capacity failure is not the problem, reliable estimation of the liquefaction-induced settlement will be of prime importance in assessment of the overall performance of the structure. Currently, there are few procedures with limited application in practice for estimation of settlement of foundations on liquefied ground. Therefore, development of a general relationship is important from the practical viewpoint. In this paper, the dynamic response of shallow foundations on liquefied soils is studied using a 3D fully coupled dynamic analysis. For verification of the numerical model, simulation of a centrifuge experiment is carried out and the analysis results are compared with the experimental measurements. The results of centrifuge experiment are taken from the literature for the purpose of comparison and the experiment has not been performed by the authors. After verification of the numerical model, a practical relationship for estimation of liquefaction-induced settlement of rigid footings on homogeneous loose to medium fine sand is proposed based on the results of a comprehensive parametric study. In the interpretation process, the soil layer thickness in which the liquefaction takes place is found to be a key parameter, since by normalization with respect to this parameter, effects of a number of other parameters can be eliminated.     

Shaking table study on liquefaction behaviour of different saturated sands reinforced by stone columns

Abstract

Liquefaction is a phenomenon developed in loose and saturated layers of sands subjected to dynamic or seismic loading, and often leads to excessive settlement and subsequent failures in structures. Several methods have been proposed to improve soil resistance against liquefaction, among which use of stone columns is one of the most applicable methods. In this research, the effect of stone columns with different geometries and arrangements on the liquefaction behaviour of loose and very loose saturated sands subjected to vibration is investigated using shaking table. Results of the experiments show that when using stone columns in sand layers, the level of maximum settlement is significantly reduced. Further, the presence of stone columns significantly reduces pore water pressure ratio. This further indicates that stone columns have a positive effect and reasonable performance, even in relatively strong earthquakes, provided that the number and cross-section of the columns are sufficient. In addition, stone columns reduce the pore water pressure dissipation time. Moreover, by increasing cross-sectional area and the number of columns, both pore water pressure and settlement decrease. Stone columns in loose sand have a greater effect on the reduction of pore water pressure compared to that of very loose sand.