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Underground water detection

 Groundwater Resources

Many regions of Thailand found suffering from drought crisis occurrence during the past year 2015 which may become worse since the last decade. The effect of climate change in 2015 lessening rainfall, the trend of drought phenomenon seems increasing in the next year 2016. Groundwater should be encountered to improve a quality of suffer community from shortening water supply in house use. Cooperative management from three factions i.e.Kasetsart University as organizer, donation companies and participant selected local communities is operated under “Kasetsart help for drought crisis” project . The budget obtained from the donation is mainly used fordrilling expend. Lao Khwan district, in particular Thung Krabum and Nong Pradu sub-district, of Kanchanaburi province was selected as a result of drought crisis region in long period and repeatedly. Four communities i.e. Ban Thung Krabum, Ban Nong Yakhao, Ban Nong Taknue and Ban Talung Nuea were precedence for this project. One emphasis condition to precede this project is the collaboration of local people and administrative offer in order to recognize and appreciate in achieved commune groundwater resource. Since most drought zone in Loa Khwan district occupied by metamorphic and granite region may indicate as very low potential of groundwater area, 2D resistivity imaging with scanning technique (Suanburi, 2010) was applied to  effectively pinpoint best aquifer location around  public zone or close to abandon commune water tank. Appropriate drilling activities such as  location for effective drill target or  deep of borehole etc. were performed following geophysical result and setting suitable submersible pump for effective consume water supply. Then water quality must be testified that may support for pertinent local people health by recommended welfare use. Setup tower tank (its height may depend on distance of distribution)for storage water and transfer to houses. Lastly, suitable water house use should be planned. The time for pumping groundwater should be regulated which is necessary to maintain water supply in sustainable utility.
1. Introduction
1.1 Background

Effect on climate change during the past year, critical drought situation is found in many regions of Thailand. The trend of drought crisis may enhance in the coming year 2016 due to a lesser amount of rainfall. To relieve water supply shorten in house consumption, groundwater supply should be the most appropriate way to improve quality of living during critical time. A new challenge managing to help suffer community was formedfrom three cooperative branches i.e. Kasetsart University as operating activities including search for donation sources, private or company who donate the budget and local communities cooperation. Cooperative and communicative task with local community is significant process to understand the project proposal and feel being the owner.
The area of Lao Khwan district of Kanchanaburi province was priority selected as a pilot project. In particular, Thung Krabum and Nong Pradu sub-district area were found as severe long period in drought crisis, occurring repeatedly and good collaboration from local community officers and people. Due to low potential of groundwater zone, water supply from groundwater resources in Loa Khwan region is more challenge to accomplish by application of successful research technique to pin point the best aquifer location in the target area. Then 2D resistivity imaging, a practically technique to investigate the nature of groundwater resources (Suanburi et al, 2007) with practical approach of scanning technique (Suanburi,2010) using Schlumberger configuration was performed with 10 m continuous shifting by 1D inversion modeling. By conceptual interpretation for groundwater resource, resistivity value may indicate type of subsurface feature, e.g. groundwater zone is in range of 30-50 ?.m where hard granite or metamorphic rock is > 100 ?.m. (Suanburi & Wathanaku , 2009) As a result, drilling for groundwater should be successful in distribution of water supply to houses which may prove that the knowledge of research can be help mass suffer local people facing drought crisis with appropriated management.
1.2 Objectives
The aims of integrate management for groundwater supply at severe drought crisis communities are to construct community-base groundwater wells with application of successful geophysical approaches for the best groundwater yield. Project management may include contribution budget for drilling and introduce local organization to manage appropriately water supply for long-term utilization.
1.3 Survey area
There are four target areas situated in of Lao Khwan district, Kanchanaburi Province, Thailand.The survey areas are located about 10-20 km South and West of Lao Khwan town and about 80 km north
of Kanchanaburi city. Three communities are governed under Thung Krabum sub district administrative organization as follows (see Figure 1).
Figure 1 Location of four communities andgroundwater map of Lao Khwan District zone.Sources: (DGR, 2006)

1) Ban  Thung  Krabum  is  set  in Silurian-Devonian metamorphic aquifer (SDmm) where the bedrock is extended from closed mountain range (metamorphic rock e.g. gneiss, schist, quartzite,
slate and marble) to the East. Topography is slightly flat and colluvial terrain with elevation of 165 m.a.s.l.
2) Ban Nong Yakhao contain groundwater feature similar to Ban Thung Krabum. Topography is slightly flat with elevation of 155 m.a.s.l.
3) Ban Nong Taknue is occupied in colluvial deposit aquifer (Qcl). Topography is flat as colluvial terrain with elevation of 65 m.a.s.l. And one community governed under Nong Pradu sub district administrative organizations is 4)  Ban Talung Nuea is found as granitic aquifer (Gr) where topography is quite flat terrain with elevation of 55 m.a.s.l.Low Potential of groundwater in SDmm and Graquifers in Lao Khwan region indicate an intensive drought circumstances during summer period. Land use around this region is mostly found as planting sugar cane and tapioca.
2. Investigating groundwater resources
Successful research technique for groundwater investigation is applied in this process using geophysical survey by resistivity measurement.
2.1.1 Principle of resistivity surveying
Resistivity reading is represented by an apparent resistivity,a calculated from observed potential value, ?V, injected current,I and geometric factor of the electrode configuration. The current
is injected into the ground at electrodes (C A , C B ) and the potential change in underground can be detected by electrode (P M , P N ). (As seen in Figure 2) (Telford et al., 1990).
Figure 2 General resistivity array positioning current electrode C A -C B and voltage probes P M -P N.

2.1.2 Vertical electrical sounding (VES) technique VES (or 1D) is a conventional method which is mostly used for groundwater exploration in Thailand. Generally, Schlumberger electrode array (for vertical changed reading) is applied by varying current electrode (AB/2 in Figure 3(a)) up to more than 300 m for target depth about 100 m.1D inversion model can be presented as high accurate interpretation (Figure 3(b)).
Figure 3 Taking VES resistivity measurement (a) and 1D inversion model (b) can indicate small fracture in bedrock (may presented as good aquifer layer).

2.1.3. 2D resistivity imaging
Resistivity automatic with 60 multi-electrode measurement is applied at the target location which obtain a geo-electrical pseudo-section over a horizontal distance of about 600 m. Measured data are found as continuous and detailed subsurface feature in both vertical and horizontal direction. Resolution of measuring technique (using Schlumberger electrode configuration) is 10 m which assume from reading station spacing of 10 m. (Explained in Figure 4).
Figure 4 Data from 2D resistivity measurement presented in section continue in both depth and along survey line.
2.1.4. Resistivity scanning technique
Apply a new technology of instrument for 2D imaging measurement then employ both 2D and 1D data processing. RES2DINV V. 3.55 program is employed for create 2D inversion geo-electrical models
which present in general subsurface view. Then 1D inversion modeling with WinSev V.6 is carried out for analyzing raw data in each 10 m apart through the whole section to identify the location of the high yield groundwater. (Suanburi, 2010).
2.2 Locating drilling position and drilling groundwater wells
Interpreted resistivity results with known hydro-geology at the survey area, best possible aquifer location (for drill groundwater) should be public and donated zone and located in vicinity to abandon commune water tank tower. Then appropriate drilling activities should follow resistivity result such as  target  deep of borehole, a number and depth of fracture zones. If unconsolidated aquifer is found, the drilling technique should be more arrangement.

2.3 Testing for the Potential of groundwater yield
The outcome of drilling may found that water yield could be different in each place due to the variation in potential and aquifer aspect. However water obtained from the drill hole is needed to testify the amount of water yield. Pumping test is necessary to know water yield which help for setting suitable submersible pump  for effective consume water supply  plan. Local administrative organization should be recommended to appropriate management in water distribution.

2.4  Observing the quality of groundwater used for water supply.
Quality of groundwater should be highly testified due to aquifer type in different hydro-geological characteristic, in particular, granitic aquifer in the project area. The utility of water in local community is
basically supposed for all activities in house use including for drinking. Then water quality must be testified that may support for pertinent local people health by recommended welfare use.
3.Successful communities-base groundwater supply
Groundwater wells have been constructed to support as commune water supply. The result of this achievement may be presented as follows:
3.1 Resistivity result
The result of resistivity interpretation with scanning technique can indicated the location of best aquifer in the target area. An examples of survey result at Ban Thung Krabum area (Figure 5), several fracture zones in hard metamorphic rock (gneiss rock) found close to main fault or fracture zone filled with weathered rock (less yield groundwater). Consequently effective drilling is success for groundwater about > 3 m 3 /hr. New water tank tower was shortly constructed at the exact location of groundwater bore well. And at Ban Talung Nuea, (Figure 6) more than 10 m 3 /hr water yield from large fracture layer is found at depth of 40m at the distance about 20m apart from the old bore hole which water yield total diminish.

Figure 5 1D & 2D inversion models can identify aquifer layer contain in fracture of bedrock at Ban Thung Krabum.
Figure 6 Thick fracture found just close to previous wells obtain large amount of water at Ban Talung Nuea.

3.2 Four groundwater-base community wells

Groundwater wells in four communities are successful to obtain water supply for house use which can besummarized in Table 1. 
Table 1 Water yield from each groundwater well and capable transport to houses.

 Groundwater Resources