Morteza Mohsenipour

Trends in rainfall and rainfall-related extremes in the east coast of peninsular Malaysia

The coastlines have been identified as the most vulnerable regions with respect to hydrological hazards as a result of climate change and variability. The east of peninsular Malaysia is not an exception for this, considering the evidence of heavy rainfall resulting in floods as an annual phenomenon and also water scarcity due to long dry spells in the region. This study examines recent trends in rainfall and rainfall- related extremes such as, maximum daily rainfall, number of rainy days, average rainfall intensity, heavy rainfall days, extreme rainfall days, and precipitation concentration index in the east coast of peninsular Malaysia. Recent 40 years (1971–2010) rainfall records from 54 stations along the east coast of peninsular Malaysia have been analyzed using the non-parametric Mann–Kendall test and the Sen’s slope method. The Monte Carlo simulation technique has been used to determine the field significance of the regional trends. The results showed that there was a substantial increase in the annual rainfall as well as the rainfall during the monsoon period. Also, there was an increase in the number of heavy rainfall days during the past four decades.

Changing Pattern of Droughts during Cropping Seasons of Bangladesh

There has been a growing concern on temporal variations on drought characteristics due to climate change. This study compares meteorological drought characteristics for two different periods to quantify the temporal changes in seasonal droughts of 18 weather stations of the country. Fifty-five years rainfall and temperature data are divided into two different thirty-year periods, 1961–1990 and 1985–2014 and standardized precipitation evapotranspiration index (SPEI) for those periods are calculated to assess the changes. Four seasons in this study are selected as two major crop growing seasons namely, Rabi (November to April) and Kharif (May to October) and two critical periods for crop growth in term of water supply namely critical Rabi (March–April) and critical Kharif (May). Results show that moderate, extreme, and severe Rabi droughts has increased in 11, 9, and 4 stations out of 18 stations, respectively, and Kharif severe and extreme droughts has increased in 8 and 9 stations, respectively, In addition, the frequency analysis shows that the return periods have decreased during 1985–2014 at the stations where it was high during 1961–1990 and vice versa. This has made the spatial distribution of return periods of droughts more uniform over the country for most of the seasons. Increased return period of droughts in highly drought prone north and northwest Bangladesh has caused decrease in average frequency of droughts. Consequently, this result corresponds that Bangladesh experiences fewer droughts in recent years. Trend analysis of rainfall and temperature data reveals that significant increase of mean temperature and no significant change in rainfall in almost all months have increased the frequency of droughts in the regions where droughts were less frequent.

Nitrate Adsorption on Clay Kaolin: Batch Tests

Soils possessing kaolin, gibbsite, goethite, and hematite particles have been found to have a natural capacity to attenuate pollution in aqueous phase. On the other hand, the hydroxyl group in soil increases anion exchange capacity under a low pH condition. The main objective of this paper was to evaluate effects of kaolin on nitrate reduction under acidic condition. In order to analyze the kaolin adsorption behaviour under various conditions, four different concentrations of nitrate, 45, 112.5, 225, and 450 , with a constant pH equal to 2, constant temperature equal to 25°C, and exposure period varying from 0 to 150 minutes were considered. The capacity of nitrate adsorption on kaolin has also been studied involving two well-known adsorption isotherm models, namely, Freundlich and Longmuir. The results revealed that approximately 25% of the nitrate present in the solution was adsorbed on clay kaolin. The laboratory experimental data revealed that Freundlich adsorption isotherm model was more accurate than Longmuir adsorption model in predicting of nitrate adsorption. Furthermore, the retardation factor of nitrate pollution in saturated zone has been found to be approximately 4 in presence of kaolin, which indicated that kaolin can be used for natural scavenger of pollution in the environment.

GIS integration of hydrogeological and geoelectrical data for groundwater potential modeling in the western part of greater Kushtia district of Bangladesh

Geographical Information System (GIS) has been used in this paper to delineate groundwater resources potential in the western part of greater Kushtia district of Bangladesh, where urgent attention for augmentation of irrigation water supply is required. Thematic maps of transmissivity, hydraulic conductivity, specific yield, net recharge, aquifer thickness, surface water bodies, aquifer resistivity, overburden aquitard thickness and its resistivity have been prepared and assigned weight according to their relative importance using Analytical Hierarchical Process for the preparation of groundwater potential model. Since the values within each thematic map vary significantly, they are classified into various ranges or types and assigned ratings. Finally, the thematic maps are integrated using GIS to prepare the groundwater potential map for the study area in terms of Ground Water Potential Index (GWPI). The evolved map indicates that 22.51% of the study area have GWPI more than 0.70 and therefore, have excellent prospective for exploitation. About 69.12% of the area with GWPI ranging from 0.50 to 0.70 is also quite promising for groundwater abstraction, while the rest 8.37% area having GWPI below 0.50 indicates moderate potential. The obtained map of groundwater potential is found in good agreement with the yields of available pumping test data.

Interference and inefficiency of water wells: a constrain of water conservation in Bangladesh

Abstract Sustainability of groundwater use for irrigation is becoming a vital concern in Bangladesh due to declination of groundwater level and escalation of irrigation cost. Groundwater exploitation in an unplanned way is considered as one of the major causes of inefficiency in groundwater abstraction. The objective of the current research is to provide a guideline of water well location planning in order to improve well efficiency and reduce irrigation cost in Bangladesh. For this purpose, systematic hydrogeological studies relating to aquifer properties, well properties, and actual location of water wells have been evaluated in a water-stressed region located in northwest Bangladesh. The results revealed that the area is potential of bulk groundwater exploitation. The well efficiency values were found to vary between 98 and 46% depending on the geology of the area. Lower efficiency values indicate that the design and well construction procedures were improper and need to be improved to obtain desired discharge. Most of the wells were interfered with each others, ultimately reduce the optimum discharge. This study concluded that the wells should be installed at least 2.5 and 1.4 km distance apart in the floodplain and Barind area, respectively, in order to avoid economic loss.

Return Periods of Extreme Meteorological Droughts during Monsoon in Bangladesh

The Objective of the Present Study is to Characterize Extreme Droughts during Monsoon (June to September) when Rain-Fed Crops are Grown in Bangladesh. Fifty Years (1963-2012) Rainfall Data Recorded at Twenty-Nine Stations in Bangladesh is Analysed Using Standardized Precipitation Index (SPI) to Reconstruct the Historical Droughts during Monsoon with Various Severities. the Extreme Droughts Events are Identified from the Reconstructed SPI Time Series and their Distribution in Time is Recognized by Fitting Various Frequency Distribution Curves. Finally, the Best Fitted Distribution is Used to Calculate the Return Periods of Extreme Droughts. the Results Show that Extreme Droughts during Monsoon Occur once in Every 18 Years in Northwest Bangladesh. it is Expected that the Study will Help in Planning Adaptation Strategies to Mitigate the Impacts of the Droughts.

Effects of El Nino Southern Oscillation on the Discharge of Kor River in Iran

The objective of the study was to investigate the El Nino forcing on the discharge of Kor River located in Maharloo-Bakhtegan basin in the Fars province of Iran. Thirty-one-year (1965–1995) and twenty-year (1975–1995) monthly mean river discharge data recorded at two stations, namely, Chamriz and Dehkadeh-Sefid, respectively, were chosen in the present study. Fourier analysis was used to extract harmonic information of time series data such as amplitude and phase angle to show the maximum effect and the time of effect of El Nino on river discharge. The study revealed that El Nino events caused increase of discharge in Kor River by 15% to 20% and the maximum influence was in the months of February and March in El Nino years.

Modeling water quality and hydrological variables using ARIMA: a case study of Johor River, Malaysia

Long-term trends in water quality and hydrological variables of natural systems reveal information about physical, chemical and biological changes and variations due to manmade and seasonal interventions. The objective of this study was to develop suitable stochastic models for predicting river water quality and hydrological variables through the establishment of dynamic relationship among the variables using transfer function modeling approaches. Autoregressive integrated moving average (ARIMA) model containing autoregressive (AR), integrated (I) and moving average (MA) was used for this purpose. The water quality variables, namely pH, color (TCU), turbidity (ppm), Al3+ (ppm), Fe2+ (ppm), NH4+ (ppm) and Mn2+ (ppm), and hydrological variables, namely rainfall and river discharge for Johor River, Malaysia, recorded for the period 2004–2007 were used in the study. Results showed that except Al3+, Fe2+, NH4+ and rainfall, all other variables are stationary. The non-stationary time series can be fitted with ARIMA (p, 1, q), while the stationary time series can be fitted with AR model with 1–5 time lags. The autocorrelations of all the samples were found within the 95% confidence bounds and the model residuals were found to follow normal probability distribution, which indicate the suitability of the models in forecasting water quality and hydrological variables. It is expected that the modeling approach developed in this paper can be replicated in other river basins for reliable prediction of river water quality due to changes in rainfall–runoff processes.