USGS: South Asia Arsenic Project Nepal

Mission

The mission of the United States Geological Survey (USGS) South Asia Arsenic Project is to conduct geohydrological and geochemical investigations in areas where natural processes produce arsenic concentrations in groundwater that exceed drinking water standards.  Drinking water containing high amounts of arsenic has adverse affects on human health, including increased risks for cancer, diabetes and heart disease.  Our investigations in Bangladesh and Nepal through a collaboration with agencies of each government is working to examine the distribution of arsenic contaminated aquifers, determine the cause of the contamination, and evaluate the ability of alternative aquifers to be sustained sources of safe water.

Fieldwork in Nepal began in February of this year to extend and apply the knowledge gained after three years of work in Bangladesh.  Although arsenicosis is currently recognized to affect many more people in Bangladesh than in Nepal, the recent increase in the use of tube wells in the Terai is likely to result in increased health risk for Nepalese citizens.  Studies in Nepal will have broad application because the rocks of the Himalayan Mountains are the probable source of the arsenic being released by sediments in India, and Bangladesh as well as in Nepal.  Thus information gathered will be relevant to evaluating problems in all of south Asia.  The initial phase of the research program in Nepal is expected to last two to three years.

Cooperation
The USGS arsenic research program in Nepal is funded by the United States Department of State (DOS), Bureau of South Asian Affairs.  It is sponsored by the Regional Environmental Office for South Asia, based at the American Embassy in Kathmandu.  The future success of the USGS program depends on close cooperation with Government of Nepal agencies and non-governmental agencies through the auspices of the National Arsenic Steering Committee (NASC) chaired by the Secretary of the Ministry of Physical Planning and Works.  Nepal Department of Water Supply and Sanitation (DWSS) is the secretariat of NASC and our primary cooperator.  USGS has relied heavily on measurements of dissolved arsenic in public and private domestic water supply wells near Parasi that was done by the district-level office of DWSS in Nawalparasi.  The Water Supply and Sanitation Division Office (WSSDO), was particularly helpful in sharing arsenic data from nearly 2500 wells tested by them in 10 villages and one municipality.    We also have been greatly assisted by the kind cooperation of the Groundwater Development Division of the Nepal Department of Irrigation (DOI), and the Environment and Public Health Organization (ENPHO).  Our work with these agencies includes a constant exchange of information without which our task would be impossible. We are grateful for their advice, insight and suggestions.

Progress
The USGS research program in Nepal this spring has, in a relatively short time, collected more than 200 samples of sediment, which is believed to be the source of arsenic in the groundwater.  These sediments were collected from the most contaminated groundwater bearing aquifers in Nepal, located in the Nawalparasi district of Lumbini Zone.  The Soil Test Consultancy contracted to help us collect intact sediment cores to depths as great as 40 m.  We also used simple local drilling methods for some test holes.  Some analyses were completed in the field, which verified that visible differences in the appearance of the sediment are related to chemical transformations linked to the levels of arsenic in the ground water in specific intervals of the sediment.   Our samples will also be sent to the laboratories of the USGS and cooperating universities for additional testing.  Critical samples were collected quickly because the areas of greatest contamination had already been pinpointed by the careful work of WSSDO Nawalparasi, a district-level branch of the DWSS.  Using arsenic analysis field kits developed by ENPHO and Global Positioning Satellite (GPS) receivers, workers in the WSSDO Nawalparasi office located nearly 2500 public and private water supply wells and determined the arsenic content in the well water and the depth of the wells.  UNICEF provided part of the financial support for this work. 

USGS was then able to use this valuable data to select sites for geotechnical coring by placing it in a Geographic Information computer system (GIS) and plotting the data points over rectified aerial photographs or topographic maps to observe the distribution of high values.  Figure 1 is an example of such a plot of DWSS data where extremely high arsenic concentrations over 200 ppb are shown as blue circles, concentrations above the Nepal drinking water standard of 50 ppb but less than 200 ppb are shown in red, concentrations within the Nepal limit but above the World Health Organization (WHO) recommended limit of 10 ppb are shown in yellow, and concentration within the WHO limit are shown in green.

Surface geology north and south of Parasi between the Himalayan Mountain front and the Indian border has been mapped by a team of USGS and DOI geologists at a scale of 1:25,000.  This data will be combined with subsurface data to construct a 3D geologic model of the aquifer system.  Most of the subsurface data was provided by the DOI Butwal office from their descriptions of sediment encountered during the drilling of the many irrigation wells they have installed in the area..  These descriptions will be interpreted in combination with those of the monitoring wells yet to be drilled by DOI and the sampling drill holes contracted and described by the USGS team.

Plans
Sediment samples collected from February to April 2003 will be analyzed during the summer months to provide guidance for the second phase of the sampling program beginning in October 2003.  As the results are collected and interpreted, preliminary findings will be shared with our Nepali partners.  Phase two will focus on another area of high arsenic concentration yet to be selected.

The USGS program is supporting and assisting in preparation of a series of maps and GIS databases summarizing the state of knowledge about the distribution of arsenic contamination throughout the twenty districts of the Nepalese Terai.  NASC has designated ENPHO to be the lead agency for compilation, although the data will be jointly owned by NASC and distributed to all its participating agencies that have contributed data.  USGS will contribute funds, technical advice, and aid in publication.  These maps will aid in identifying the extent of impacted areas and thus be a guide for mitigation efforts.

USGS will assist DOI and World Bank in installing two sets of monitoring wells in Parasi to measure variations in arsenic concentrations in water between various aquifers, and variations in concentration over time.  We will provide technical advice on installation of the well seals and geochemical information on the likelihood of local aquifer sediments releasing arsenic in the area of the monitoring wells.