This book on water quality issues in Asia is based on two main components: one is the invited contributions from experts specially for this book; and second is related contributions already published in the Asian Journal of Water, Environment and Pollution in recent years after peer review process. In addition to Asian region, attempts have also been made to include some case studies outside Asia such as Africa and U.K. to give an integrated approach to understand the Asian problems specifically related to the water sector.

The first chapter (Controlling Factors in River Water Quality in Asia) authored by the editor discusses current state of our knowledge regarding continental input to adjacent coastal regions in south Asia. Though natural process of weathering contributes many constituents to water, the increasing population pressure and supply-demand gap has made the water scenario very critical in quantitative as well as qualitative terms due to unprocessed effluents flowing into natural water bodies and then to the coastal oceans.

The second chapter (Reclaimed Opencast Coal Lands in Southeast Wales: Impacts on Water Quality) is contributed by experts from U.K. who have worked on changing water quality due to coal mining that has serious implication for countries in Asia, particularly China, India and Indonesia–all of whom depend for the most part on coal for their energy needs. The main impact of former opencast sites on river water quality is likely to come through diffuse pollution from the zone of aeration and water table fluctuation zone in the body of the buried spoils. Although this zone is mainly detached from the surface hydrological system and deprived of rainwater infiltration by the impermeability of the surface layers on these sites, the lateral percolation of groundwater from offsite through the crushed rocks of the spoil is very likely to pick up many heavy metals from chemically active sites.

The third chapter (Coastal Pollution Loading and Water Quality Criteria–Bay of Bengal Coast of India) is based on a consolidated report prepared by experts on sustainable coastal environment. The Bay of Bengal Ecosystem has been identified as one of the world's sixty-four Ecosystems (LMEs–Large Marine Ecosystems) sharing a distinct bathymetry, hydrography, productivity, and tropically dependent population and involves eight littoral countries, with the primary goal of enhancing the livelihood security of coastal population of these countries. This chapter is based on individual country's contribution to the international co-ordinated project.

Next chapter (Applications of GIS Remote Sensing for Sustainable Use and Management of Groundwater: A Case Study from the Northwestern Coastal Area of Sri Lanka) by experts from Sri Lanka specially focusses on groundwater quality issues due to coastal salt water infiltration. Thirteen hydrogeochemical parameters of 150 locations in both Kalpitiya and Mannar areas were analyzed for the samples collected both from dug wells and shallow tube wells; and resistivity imaging technique were also applied to access the groundwater contamination due to seawater intrusion and resultant quality changes in inland waters.

The fifth chapter (Influence of Solid Waste Disposal Conditions on Organic Pollutants Discharged from Tropical Landfill) is written by experts from Thailand on pollutant transfer from waste disposal sites to ground water. Several factors were investigated including waste composition, compaction density, rainfall intensity, leachate re-circulation and accumulation of leachate in the waste cell. The collected leachate samples were determined for chemical characteristics. Leachate re-circulation was practiced to investigate incremental leaching of pollutants along the waste depth.

Chapter 6 (Impact of Industrial Effluents of Gadoon Amazi Industries over Quality of Ground Water: A Case Study) is related to studies in Pakistan on water quality. Authors have tried to correlate the deterioration of ground water by the industries quantitatively. The ground water is not fit for drinking purpose. The effluents are highly polluted and not fit for irrigation purpose.

Chapter 7 (Groundwater of the Municipalities of Southwestern Coastal Bangladesh) gives a comprehensive review which endeavours to elucidate the geochemistry of solute load of such aquifers for its monitoring, management and conservation. Aquifers of the urban conglomerates in coastal Bangladesh are vulnerable in terms of quality and quantity. 170 groundwater samples from the production tube wells, penetrating mostly the shallow coastal alluvial aquifers, collected in different periods are analyzed for major cations and anions following standard methods. The spatial variation of solute load to the aquifers is statistically quite significant.

In chapter 8 (Application of Multivariate Statistical Analysis to Define Water Quality in Jajrud River) the ground water quality in Iran is discussed in detail. The copious prevalence of water deficiency and the geographical location of Iran make acquiring enough accurate data of water quantity and quality for water management vital. In this work, statistical method was used to analyze the data collected from the catchment area under study. The study also shows that ground water is the first effective factor. Domestic waste water pollution is the second-most important factor. Agricultural fertilizers and industrial waste may rank as the third and fourth pollution factors, respectively.

Poor water quality due to sewage pollution in Cambodia is discussed in chapter 9 (Efficiency of Phnom Penh's Natural Wetlands in Treating Wastewater Discharges). Water quality samples were collected in three sewer channels and at two longitudinal sites within the wetland principally during the dry season. Several contaminants within the sewer channels were significantly diluted by stormwater during individual rain events, although this trend was not observed within the wetland.

Chapter 10 “Water Quality of the Chao Phraya River” deals with the variation of water quality along the distance of the river and seasons before flowing into the Gulf of Thailand. Only 22% of water samples reached officially established standard. The hypothesis testing found that the distance along the route of water mass had relationship with water quality. Thus spatial variability in water quality is an important factor in river water chemistry.

Chapter 11 (Well Drinking Water Fluoride Content and Dental Fluorosis in Al-Butana Region of Central Sudan) gives an insight into the fluoride problem in Sudan. In this study the F^- ion concentration levels of209 wellwater samples belonging to previous construction analysis and a total of 121 well water samples belonging to the current study in Al-Butana region of Central Sudan were investigated and mapped using the geographical information system (GIS).

Chapter 12 (Evaluation of the Quality of Drinking Water in Kerala State) deals with water quality in the coastal region bordering the Arabian Sea. The quality of tap water from water supplies from 14 districts of Kerala state, India was studied. Parameters like pH, water temperature, total dissolved solids, salinity, nitrates, chloride, hardness, magnesium, calcium, sodium, potassium, fluoride, sulphate, phosphates, and coliform bacteria were enumerated. The results showed that all water samples were contaminated by coliform bacteria.

“Stable Carbon and Nitrogen Isotopes as Indicators of Organic Matter Sources in Ishikari River System” addresses in chapter 13 isotopic aspects of water chemistry in Japan. The bed sediment and particulate organic matter samples collected from Ishikari River and its tributaries were analyzed for organic C, total N and their isotopic composition. The study shows strong inverse relation with the dissolved nitrate concentration in the lake water indicating that significant portion of the POM being derived from phytoplankton that were utilizing nitrate that had been subjected to denitrification.

The Himalayan watershed in Nepal has been studied in chapter 14 (Water Quality and Flux of Bagmati River within Kathmandu Valley, Nepal). Water sampling was carried out along the heavily urbanized Bagmati drainage network within Kathmandu valley during 2010-2011 in order to evaluate the controlling factors of chemical parameters and to estimate the transport of chemicals from different positions of the landscape. Most of the chemical parameters appeared to increase their concentration with distance downstream.

This book will be of interest to all serious water specialists, researchers and policy makers because Asia encompasses a myriad of water related problems. Experts who have contributed in Surface and Sub-surface Water in Asia make a serious effort in addressing these issues and the attempts made in resolving them is indeed a learning experience for all.