Water quality and wastewater
In Southeast Asia, management of wastewater, or lack thereof, has posed a major problem and contamination issue to groundwater and surface waters (ADB
2013). In Myanmar, wastewater is considered to be the most important water quality issue in urban areas such as Mandalay and the Amarapura Township (ADB
2013; Moe
2013; UNDP
2014). In this study, the water quality of the Amarapura Aquifer was examined to determine if the main source of pollution is wastewater. Na-Cl water types have been observed in many groundwater systems that were contaminated with urban wastewaters (Bashir et al.
2015; Hassane et al.
2016; Lee et al.
2010). In this study, Na-Cl water types were observed, and water quality parameters determined elevated levels of total dissolved solids, electrical conductivity, chloride, nitrate, ammonium, and
E. coli. These water quality parameters have been used to indicate contamination of groundwater from wastewater sources (Bajjali et al.
2015; Hassane et al.
2016; Lawrence et al.
2000; Lee et al.
2010; Nagarajan et al.
2010; Nas and Berktay
2010). The Cl/Br ratio has also been used as a key parameter to determine the extent of groundwater contamination from wastewater sources (Vengosh and Pankratov
1998). From a combination of these factors, it is determined that wastewater from local sewage canals contaminates shallow wells in the Amarapura Aquifer.
Previous studies on wastewater contamination of groundwater in other regions of the world have resulted in similar water types, for example Na-Cl (Bashir et al.
2015; Hassane et al.
2016; Lee et al.
2010). Geochemistry data yield a predominant Na-Cl water type across the Amarapura Aquifer, which is most likely the result of infiltration by urban wastewaters because there is no known local source of halite. Not being in an arid environment, it is unlikely that evaporation would play a major role in the precipitation of Na-Cl.
In sampling of the Irrawaddy River, a Ca-SO
4 water type is observed towards the north side of the river during both the wet and dry seasons. During the dry season, sampling was extended farther south, revealing a change in water type to Ca-CO
3. It is believed this is the dominant water type because of the local calcite deposits, and the sulfate anions are influenced in these surface waters from the weathering of barite (Adamu et al.
2014; Baldi et al.
1996).
Myanmar has begun development of its industrial infrastructure with help from other countries across the region and world. The water quality data presented here can serve as a baseline for future development. Many sources of pollution still exist within Mandalay. The water quality data and an uneven spatial distribution and high concentration of other ions such as ammonium, nitrate, and chloride suggest that this likely results from anthropogenic wastewater sources. The presence of ammonium, nitrate above 10 ppm, and chloride above 100 ppm typically indicates influence from domestic wastewater (Fetter
1999). High sulfate levels are also observed but are likely from barite (BaSO
4) deposits in the Shan Plateau. It is expected that calcite (CaCO
3) and barite (BaSO
4) would be the dominant water types in this area because they are present in the local source rocks.
Another indicator of anthropogenic waste is
E. coli, whose presence is commonly related to human waste, can cause severe diarrhea, and is often associated with other waterborne pathogens (WHO
2008). In Myanmar, it is estimated that 38 children per 1,000 live births (3.8%) die before the age of 5, which is mainly attributed to waterborne diseases and malnutrition (Pavelic et al.
2015). During the wet season, 100% of dug wells and 33% of tube wells sampled contained unsafe levels of
E. coli for drinking water. During the dry season, 86% of dug wells and 11% of tube wells sampled contained unsafe levels of
E. coli for drinking water. High levels of
E. coli in these wells may be due to wastewater canals or poor hygiene practices by those using the wells. DW10, being within 5 m of the Shwe-Ta-Chaung sewage canal, is more likely to have been contaminated by local wastewater. Locals using water from this well knew not to drink the water but still used it for cleaning dishes and taking baths, which could still potentially pose a health risk.
A few groundwater wells had different water types between seasons (YDB1, SVD, SA2, and DW4) and are likely due to contamination from other anthropogenic sources because of improper well construction. YDB1 changed water types between seasons from Na-SO4 during the wet season to Ca-CO3 during the dry season, likely due to overland flow of water during the wet season going directly into the well. YDB1 only has about 3 cm of stick up and is covered with brick, which does not protect it from water flowing into it when flash floods are above 3 cm, which occurs frequently during the monsoon season. CaCO3 is consistent with the dominant water type suspected to be present in this system, especially in deeper wells, because there is evidence of calcite deposits in this area. The water type in SVD changed from Na-HCO3 to Na-Cl, which may be due to changing groundwater flow directions between seasons near TTML. The water type in SA2 changed from Ca-Cl to Na-Cl between seasons, but this was a minor change that plots very close to one another on the Piper diagram and is not significant. The water type in DW4 changed from Na-Cl to Ca-Cl but was also a minor change on the Piper diagram.
Contamination of the shallow aquifer system can have a negative impact on the health of those using water from dug and tube wells in the Amarapura Township. It is possible that many of these health effects have gone unnoticed because health surveys have not been conducted. Local infrastructure is needed to build lined wastewater canals or underground sewers to protect water sources, and treatment plants are needed, which has been shown to reduce wastewater’s impact on shallow groundwater systems (Foster et al.
2011). Numerical modeling can be used as guidance for resource management and determining protective zones for wells (Foster et al.
2011). A safe and accessible municipal supply would also reduce the number of private wells being used and make management strategies more controlled (Foster et al.
2011). Other small things can be done as short-term solutions such as building concrete pads that direct wash and wastewater next to a well away from it and into a lined canal (Schneider
2014; Danert
2009). Better construction of deeper tube wells can also help to improve the quality of the water people in the Amarapura Township are drinking (Schneider
2014; Danert
2009).
One of the goals of this project was to determine if inexpensive and easy-to-use chemical analysis kits could be used in the developing or low-income countries. The advantages of these kits are that many analyses could be performed for tens of dollars versus the multi-thousands of dollars needed for laboratory analyses, especially in a country with limited electricity, Internet, and access to reagents. While the kits’ results were not an exact match for the IC results, the same trends were observed. The kits allow one to determine water samples that have high concentrations of specific ions which could then be sent to a laboratory. The kits were also easy to use and allowed for many different faculty and graduate students at universities to learn more about geochemistry and their water supply.
Well construction
Well construction is often a major issue in the developing world when trying to provide clean water to those living there. Dug and tube wells both present issues with their construction that make them vulnerable to contamination. Variations and combinations of cable tool percussion, air rotary, mud rotary, auger, and reverse circulatory rotary are often used to construct groundwater wells (Schneider
2014), while commonly used in Myanmar’s rural area is manual percussion and the sludging method (Danert
2009). Well construction is a very important aspect to supplying and maintaining clean water in these areas. With the proper information and materials, simple improvements can be made to improve the construction of tube wells and further improve the quality of groundwater used, a change that could impact 68% of domestic water usage in the Amarapura Township (Moe
2013).
While dug wells are not usually used for drinking, they had been constructed with brick liners for over 50 years ago. Typically, the bottom of the dug wells was just naturally occurring sand layers with no existing covers for the wells, leaving them vulnerable to debris collecting inside them. Additionally, the large diameter, heavy usage, and local hygiene practices left dug wells vulnerable to surface contaminants. Since the local population depends on dug wells, water quality could be improved by pumping water from the well and collecting it in closed containers, where chlorination could be used as a treatment. Covering the dug wells and extending concrete pads on top to divert used water away from the well would also help to improve the water quality.
Tube wells did not contain any kind of sand pack, grouting, or annular surface seal to prevent infiltration of surface contaminants directly to the screen of the tube well (Schneider
2014; Danert
2009). Many of these did not contain a cap, and YDB1 had a stick up of only 3 cm, leaving it vulnerable to overland flow. Often, during construction, unfiltered/unclean water from local ponds was dumped down the well, and no well development was attempted.
Many locals install tube wells because they know they provide better drinking water quality. Tube wells are safer than dug wells for drinking water purposes because they are deeper and have a screened interval. They also do not have buckets being dumped directly into them to retrieve water but instead have a hand or compressor pump, although this was not always the case. Many of the wells with varying water chemistry between seasons are tube wells, which is likely due to the way in which they were constructed. More importantly is the utilization of a well pad/apron, particularly as the drilling method may have made installation of a sanitary seal in the annulus difficult. Without a proper sand pack or grout in the annulus, many of these wells have open space between the surficial material and the well casing, making these tube wells vulnerable to contamination, especially when there is a high amount of overland flow from rain or from practices of washing and cleaning directly next to the well. During the dry season, water chemistry revealed water types similar to the surrounding geology, suggesting that a higher amount of contamination occurs during the wet season.
Groundwater flow
The groundwater flow models of the Amarapura area are the first of any kind in the country of Myanmar. Little is known about the local groundwater flow systems and the variability that may exist between seasons or the influences from TTML and the Irrawaddy River. The physical conditions of an aquifer play a major role in the potential contamination of the groundwater from the surface because this controls the wastewater’s ability to penetrate the subsurface. These models were used to provide additional understanding of this regional groundwater system. Improvements can be made, but these models provide information on key characteristics of the Amarapura Aquifer, which can be further investigated for a better calibration in future studies.
The physical hydrogeology of an area plays an important role regarding the potential for surface contaminants to infiltrate into the shallow Amarapura Aquifer. The Amarapura Aquifer contains predominantly coarse–medium sands with gravels, which creates a wide range of hydraulic conductivities. Its high average hydraulic conductivity (67 m/day) and high average linear velocity (2.10 m/day) allow water/contaminants to flow in and out of the aquifer. The surface water to groundwater interaction was observed by changing heads in response to changing weather conditions (Haitjema
2012). Heavy thunderstorms and prolonged rain events cause additional inflow of water from the Irrawaddy River and other surface-water features in the region.
The analytic element groundwater flow models showed the conceptual model to be correct, and groundwater does predominantly flow towards the Irrawaddy River. Sensitivity analysis showed hydraulic conductivity to be a key physical characteristic of this groundwater flow system. In the model calibration, four hydraulic conductivity zones were identified (see Fig.
7). Sensitivity analysis also showed the lake stage of TTML to be a major factor in the model calibration. When the head of TTML was raised 1–2 m, there was an improvement in the model calibration, which could be due to the potential 2–3 m error in the digital elevation model in assigning these head measurements. Errors in the digital elevation model have been observed in another study, especially with smaller streams (Frederick et al.
2006). However, in general, flow directions and groundwater divides did not change significantly with this elevated head in TTML. Results for recharge, hydraulic conductivity, and average linear groundwater flow velocities in the model provided results within the same order of magnitude as the field measurements, which further validated the final model and assumptions provided by the sensitivity analysis and the PEST module.
Seasonal differences in groundwater flow existed between the dry and wet season models. The dry season model showed the influence of TTML on the shallow groundwater system, which creates a groundwater divide between TTML and the Irrawaddy River. However, this groundwater divide is not seen in the wet season model when heads are higher. Groundwater gradients also spread farther apart during the wet season and show slower average groundwater linear velocities. This groundwater divide likely disappears because of a less permeable sediment layer at a particular head or because, with such a high influx of water, during the wet season the influence of TTML becomes negligible. This means that when more water is added to the system during the wet season, groundwater and surface-water heads are more consistent across the region, potentially allowing for rapidly rising heads in TTML and the Irrawaddy River during monsoon rain events to cause reverse flow conditions for short periods of time (2–10 days).
Modeling results were also used to compare geochemical differences across the site between seasons. As presented earlier, there were very few major geochemical differences and these were not suspected to be a result of physical flow differences; however, at the beginning of this project, electrical conductivity measurements were used in identifying the potential groundwater divide. During modeling, the hydraulic conductivity zones around TTML were identified and showed similar geochemical characteristics. Wells in the low hydraulic conductivity zone (K2) near TTML typically had a lower TDS, whereas wells in the higher hydraulic conductivity zone (K3) near TTML typically had a higher TDS. These zones around the lake should be considered in future conceptual models of this area and tested further to determine their validity. Future models could also investigate specific contaminants in specific wastewater canals to determine whether the contaminants are traveling along these groundwater flow paths and infiltrating into the local wells.
This initial model provides a general characterization of the regional groundwater flow. Many improvements would be needed to improve the accuracy of the calibration such as properly surveying wells, long-term monitoring of surface-water heads/stages, and a watershed model for the Irrawaddy River. Additionally, from the transient conditions observed and fast groundwater velocities, an improved time-series monitoring system of groundwater heads, surface water heads, and velocities of the rivers/streams would be needed to accurately determine the full extent to which the Irrawaddy River influences flow conditions in the Amarapura Aquifer during the wet season.
Open-source software
Open-source software such as GFLOW and QGIS were used in this project because they are free and do not require licenses. QGIS contains numerous instructional videos and documents that give assistance on how to use the software (Quantum Geographic Information System
2016), while GFLOW contains instructional documents that assist using the software and understanding the assumptions made in the groundwater model (Haitjema
2016). The software is just as effective as using any other software that could have been chosen for the tasks necessary in this project but contained challenges when transferring this information to local professors in Myanmar, such as in regards to Internet access and language barriers.
Many of the challenges in a country like Myanmar concern accessibility. Even when the technology is available, other services such as Internet service are not. The Internet service in Mandalay is still very slow and often nonfunctioning, which makes downloading large software files difficult and often impossible. Access to the Internet is only available during regular work hours at the university but technical problems and blackouts mean that the Internet often does not work. QGIS contains many help videos, but prohibitive loading times prevent viewing. Open-source maps such as Google maps, are often blocked by government Internet services or technology. QGIS is moderately technical and difficult to teach in a short course to non-English speakers; additionally, the instructional videos and documents are in English, which not everyone can understand. GFLOW is very technical and requires a basic understanding of groundwater modeling; however, many of the local geology professors are just receiving their first course on the basics of hydrogeology, which causes another barrier.
Improved accessibility to these materials is needed to be successful for projects such as this one to start improving research and site investigations in Myanmar. During the second trip many of these problems were solved by bringing flash drives pre-loaded with all of the software and materials. Open-source software is a great starting point for universities such as Yadanabon University to start producing higher quality research, but more support is needed locally. Local investment and commitment to projects such as this are needed for them to be successful in the future and to continue to improve in the field of hydrogeology in Myanamar.