Drinking Water Quality Study of Tube Wells in Kandal Province, Cambodia – Guidance Summary

 

Resource Development International Cambodia (RDI)

Thousands of wells are drilled in Cambodia each year, with the goal of supplying safe and accessible drinking water. The availability of clean drinking water is a basic right of all peoples.  Unfortunately, many of these wells offer water which is either unsafe for human consumption and/or has such poor aesthetic quality that no one will consume it.  Despite the potential magnitude of this problem, very little data has been gathered to prevent the senseless poisoning of villagers and the wasting of millions of dollars constructing wells that yield water of inferior quality. 

In response to the need for an appropriate guidance tool, a drinking water quality guidence model has been developed by RDI and implemented for Kandal Province.  Approximately 2,400 samples were collected throughout the province, and tested and analyzed at RDI’s laboratory facility.  Guidance is provided and presented in three unique ways.  First, a drinking water quality index (DWQI) has been calculated for each commune.  A DWQI provides a simplified but powerful representation of the health and aesthetic conditions of drinking water within a spatial boundary.  A health value represents the safety of the drinking water, and a letter grade reflects the potential acceptability of the water in terms of aesthetics (i.e. taste and appearance).  Some communities learn to live with generally distasteful and displeasing water, but in some cases measures can be taken to improve its acceptability.  Second, statistical analysis has been performed to determine the probability of encountering  unsafe or unacceptable water.  Third, mapping tools have been utilized to present spatial interpretations of the data at both large and small scales.  Sample locations are presented on a large-scale commune map, and samples that exhibit elevated concentrations of health parameters are colour-coded appropriately.  Small-scale province maps have been developed to provide insight into regional conditions and trends for each parameter.  Also, risk maps have been generated which link population density to concentrations of health-related parameters.  These guidance tools are presented in the province maps and in reports generated for all 147 communes in Kandal Province.  The technical detail of the survey and its analysis have not been eliminated, but harnessed in such a way that it can be utilized as a simple, yet valuable decision-making tool. 

Altogether, the guidance provided in this report will allow end-users to make decisions that ensure funding is used appropriately and lives are not needlessly put at risk.  Additionally, regions that already exhibit drinking water problems can be properly targeted and appropriate drinking water sources can be determined. 

The following instructions are provided to assist with the analysis of the guidance provided in this report.
 

Guidance Instructions 

Drinking water quality guidance is provided in three forms: the DWQI, statistical analysis (probabilities), and spatial analysis.  This section provides the information required to interpret these guidance tools accurately and effectively.  If used correctly, the end result is a decision that is cost-effective and ensures the safety of Cambodian populations. 

Applicability – The guidance in this report only applies to tube wells in Kandal Province, Cambodia.  Tube wells are drilled into aquifers at a depth of 20-90 meters, and are often fitted with a hand pump.  Tube wells can provide long-lasting, clean, and safe drinking water when implemented properly.  If placed in an inappropriate location, tube wells can provide unsafe or unacceptable drinking water.  In such cases, alternative water sources could include rainwater, surface water (rivers, wetlands, or lakes), or shallow aquifer water (open/hand-dug wells).

 Drinking Water Quality Index (DWQI) – A DWQI is calculated and presented for each commune.  It is a representation of the drinking water quality in the commune based on the parameters chosen for analysis (Arsenic, Manganese, Fluoride, Nitrate, E. coli, Iron, Turbidity, Hardness, Chloride, and pH).  The index is broken up into a health value and an aesthetic letter grade.  A health value less than or equal to 60 indicates that there is a high risk of encountering unsafe drinking water if a tube well is placed in the commune.  As health values increase from 60 to 100, this risk decreases.  While no area can be assumed to be completely safe the higher the DWQI is, the less likely unsafe water will be encountered.  DWQIs marked with an asterisk indicate that fewer than 10 samples were collected within the commune.  This is generally caused by the absence of tube wells within the commune. 

Probabilities – When a sample collected in the field exceeded drinking water standards for a particular parameter, the parameter was subsequently considered a ‘Parameter of Potential Concern’ for the commune where the sample was collected.  Parameters of Potential Concern are presented in the commune reports, along with the corresponding probability of it being encountered above unsafe or unacceptable levels. 

Spatial Analysis (Sample Locations) – In each commune report, the location of the samples collected are presented on a topographic commune map. It is important to understand that the DWQI and probabilities are based on data from sample locations in the commune. It should also be noted that data may not have been collected in some portions of the commune, due to poor accessibility or the lack of wells in some areas. Thus, special consideration must be given if a well is to be placed in an area poorly represented by the sample locations.  Special consideration must also be given when contaminations are restricted to localized portions of the commune, as the DWQI and probabilities represent all the data. 

Spatial Analysis (Provincial Maps) – Provincial maps are presented outside of the commune reports.  Small-scale maps have been created for the DWQI and tested parameters, representing data for every commune in Kandal Province.  These maps are useful in observing regional trends and defining areas of unsafe or poor groundwater conditions.  Risk maps have been developed which combine population density and concentrations of health-based parameters. 

Altogether, these analysis methods provide an accurate, simplified, and powerful guidance tool.  RDI intends to secure funding to complete similar analysis for the remaining provinces of Cambodia, as wells as expanding it to include shallow aquifers and surface water.