Capability of ETM+ in estimates standing stock in beech stands of mountain forest

Stand volume is an important criterion in forest sciences for monitoring status and function of forests, estimation of productivity, prediction and modeling of forest disturbance, economic and environmental issues, and forest planning. The aim of this research is to evaluate the ETM+ sensor of Landsat 7 satellite data ability for forest timber volume estimation. For this purpose, 40 selective sample plots with 60?×?60 m dimension were selected, and in each sample plot, standing volume was calculated. Correspondent digital data to plots were extracted from spectral and considered as independent variables. Original stand volume data, square root, and logarithm of them were considered as dependent potential for stand volume estimation. Variables using stepwise regression, the best model with coefficient of determination, and adjusted coefficient of determination with regard to determining the appropriate model were modified Log?V=?07.546?+?0.85Greenness???10.564NDWI???28 0.063Band1. In this model, the coefficient of determination and adjusted coefficient of determination were obtained 0.778 and 0.770, respectively. Result showed that spectral data of the mentioned sensor have a moderate.     

Determination of Key Beds from the Cap Rocks of Oil Reservoirs Using a Novel Method,Case Study: The Gachsaran Formation,Southwest Iran

Lithology and Mineral Resources - The use of key beds in the cap rocks of the oil reservoirs is crucial. Lack of awareness of these key beds will have serious risks and damages. The Gachsaran oil...     

Spatial variability of climatic hazards in Bangladesh

Natural Hazards - Climate change is evident with the extreme climatic indices changing all over the world. Bangladesh is one of the most vulnerable countries to climate change. The patterns of...     

Long-term trend analysis of water table using ‘MAKESENS’ model and sustainability of groundwater resources in drought prone Barind area,NW Bangladesh

In Bangladesh, agriculture plays a major role in the national economy. In the drought prone Barind area in NW Bangladesh, cropping intensity has increased almost double since late eighties of last century (from 1985) because of the introduction of groundwater irrigation. Long-term behavior of groundwater table (GWT) in the drought prone Barind area has been studied using MAKESENS model in the wake of massive installation of tube-wells. The study reveals that the maximum and minimum depths to GWT during 1991-2010 show on average declining trend of 4.51 m and 4.73 m. The long-term prediction for the period of 2020-50 assuming the current rate of groundwater withdrawal is that the declining trend will be 1.16 to 1.59 and 1.07 to 1.82 times more for maximum and minimum groundwater depths respectively in comparison to the present. The rigorous exploitation of groundwater for irrigation, decreasing rainfall and surface geological attributes lead towards declining trend of GWT. This will hamper the country’s food security and ultimately threaten its socio-economic sustainability. So the appropriate strategies for the management of groundwater resource on a sustainable basis should be the priority for maintaining agricultural productivity.     

Climates of urbanization: local experiences of water security,conflict and cooperation in peri-urban South-Asia

ABSTRACT

This article explores changing water (in)securities in a context of urbanization and climate change in the peri-urban spaces of four South-Asian cities: Khulna (Bangladesh), Gurugram and Hyderabad (India), and Kathmandu (Nepal). As awareness of water challenges like intensifying use, deteriorating quality and climate change is growing, water security gets more scientific and policy attention. However, in peri-urban areas, the dynamic zones between the urban and the rural, it remains under-researched, despite the specific characteristics of these spaces: intensifying flows of goods, resources, people, and technologies; diversifying uses of, and growing pressures on land and water; and complex and often contradictory governance and jurisdictional institutions. This article analyses local experiences of water (in-)security, conflict and cooperation in relation to existing policies. It uses insights from the analysis of the case studies as a point of departure for a critical reflection on whether a ‘community resilience’ discourse contributes to better understanding these cases of water insecurity and conflict, and to better policy solutions. The authors argue that a community resilience focus risks neglecting important insights about how peri-urban water insecurity problems are experienced by peri-urban populations and produced or reproduced in specific socio-economic, political and policy contexts. Unless supported by in-depth hydro-social research, such a focus may depoliticize basically political questions of water (re) allocation, prioritization, and access for marginalized groups. Therefore, the authors plead for more critical awareness among researchers and policy-makers of the consequences of using a ‘community resilience’ discourse for making sense of peri-urban water (in-)security.

Key policy insights

• There is an urgent need for more (critical) policy and scientific attention to peri-urban water insecurity, conflict, and climate change.

• Although a changing climate will likely play a role, more attention is needed to how water insecurities and vulnerabilities in South Asia are socially produced.

• Researchers and policy-makers should avoid using depoliticized (community) resilience approaches for basically socio-political problems.

     

Hydrogeological characteristics of waterlogged areas in Natore District,Bangladesh

Waterlogging (WL) refers to the process by which water flow is resisted in vertical and horizontal directions and thus water stagnates for a short or long span of time; it is induced by a combination of human and natural factors. In the southwestern region of Bangladesh, including Natore District, WL is a significant issue that needs to be addressed if agricultural activity is to be successful. This study aimed to identify surface WL in Natore District and to characterise the WL scenario in the study area in terms of hydrogeology. Waterlogged areas were identified with a geographic information system using satellite images corresponding to the premonsoon and postmonsoon periods. Using groundwater level data (1990–2017), the pre- and postmonsoon scenarios of the waterlogged areas were indicated by seasonal and perennial types of WL. Groundwater recharge scenarios were classified as long and short lag times. Most of the study area was characterised by thick clay or silty clay surficial layers with low water penetration rates, resulting from low porosity and low hydraulic conductivity. The cross-correlation between rainfall and groundwater level revealed the response of groundwater to rainfall, with a lag time of 1–5 months. Long lag time areas exhibited slow groundwater recharge and significant groundwater level fluctuation, with lower hydraulic conductivity values of 49.37–76.24 m/day. In contrast, short lag time areas displayed rapid groundwater recharge and small groundwater fluctuation due to a good proportional relationship with rainfall and higher hydraulic conductivity values of 74.74–117.79 m/day.

     

Arsenic remediation by Australian laterites

The efficiency of Australian laterites in arsenic adsorption has been examined using three laterite samples collected from different locations in South Australia. The characteristics such as electrical conductivity, pH, mineral compositions, and isoelectric point of laterite samples have been measured. The laterite samples are mainly composed of iron and aluminum oxides, and rutile (TiO₂). Two batch experiments have been performed to compare the efficiencies of different laterites to remove AS (III) from water at two different doses, and to examine whether pH influences arsenic adsorption. For 50 mg/l arsenic solution, at doses 1,000 g (laterite)/l (arsenic solution) and 200 g/l, the laterites removed more than 97% and 87–97%, respectively. At the dose of 200 g/l, adsorption capacity has been found to be 200–243 mg/kg. Out of the laterite samples from three localities, the Kangaroo Island laterite performed the best. This is probably related to its high content of gibbsite. It has been found that arsenic adsorption by laterite is not significantly affected at the examined pH ranges of 4.7–10.0.     

Hydrochemistry and origin of salinity in groundwater in parts of Lower Tista Floodplain,northwest Bangladesh

Hydrochemistry in parts of the Lower Tista Floodplain in northwest Bangladesh is dominated by alkalies and weakly acid, having highest concentration of sodium cations and bicarbonate anions respectively. Groundwater is characterized by sodium-calcium and sodium-potassium cation and bicarbonate-chloride-sulphate anion facies, and genetically ‘normal chloride’, ‘normal sulphate’, and ‘normal carbonated’ type, and soft to saline. Based on electrical conductivity values, the area is divided into northern fresh and southern saline groundwater zone, and values like salinity, Na%, SAR, and RSC and a good correlation between Na⁺ and Cl^?, and Cl^? and salinity reveals increasing salinity with depth indicating a mixing of fresh and saline bodies due to marine transgression (?) during Holocene period in the Bengal delta. The rock weathering is likely to affect the groundwater quality by dolomite dissolution and calcium precipitation, representing reverse softening process and is brine seawater. Water extracted from shallow zone (from 20 to 30 m) has suitability for drinking purpose, livestock consumption and irrigation purposes, and partially suitable for industrial use, but that from deeper zone (from 30 to 50 m) is generally poor and unsuitable especially for irrigation purposes with low alkali and moderate to high salinity hazard. So groundwater can be used for irrigation in the area of fine textured soil with proper management practices.     

A numerical technique for simulation of the effect of soil nitrogen transport and transformations on groundwater contamination

Two numerical models, one for the vadose zone and the other for the aquifer system, are utilized to predict nitrate pollution potential in groundwater. Transport by dispersion and convection of mobile species of nitrogen, ammonium ion exchange, first order nitrogen transformations, and nitrogen plant uptake are included in the formulation for the vadose zone. Transport of nitrate in the aquifer is assumed to be affected only by dispersion-convection phenomena. Justifications for one-dimensional conceptualization of flow in the vadose zone and two-dimensional representation for the aquifer, under various field conditions, are presented. To illustrate the concept, a simple hypothetical problem is solved. The approach presented here provides an efficient means of long-term simulation of large-scale field problems.     

Drought analysis and its implication in sustainable water resource management in Barind area,Bangladesh

The study analyzes drought using Standardized Precipitation Index (SPI) and Mann-Kendall (MK) Trend Test in the context of the impacts of drought on groundwater table (GWT) during the period 1971-2011 in the Barind area, Bangladesh. The area experienced twelve moderate to extreme agricultural droughts in the years 1972, 1975, 1979, 1982, 1986, 1989, 1992, 1994, 2003, 2005, 2009 and 2010. Some of them coincide with El Niño events. Hydrological drought also occurred almost in the same years. However, relationship between all drought events and El Niño is not clear. Southern and central parts of the area frequently suffer from hydrological drought, northern part is affected by agricultural drought. Trends in SPI values indicate that the area has an insignificant trend towards drought, and numbers of mild and moderate drought are increasing. GWT depth shows strong correlation with rainy season SPI values such that GWT regaining corresponds with rising SPI values and vice versa. However, 2000 onwards, GWT depth is continuously increasing even with positive SPI values. This is due to over-exploitation of groundwater and changes in cropping patterns. Agricultural practice in Barind area based on groundwater irrigation is vulnerable to drought. Hence, adaptation measures to minimize effects of drought on groundwater ought to be taken.