1:50,000 Scale Groundwater Resource Mapping and Vulnerability Assessment in the Municipality of Kalawit, Zamboanga del Norte [Progress Report]

The Phase-IV of the 1:50:000 Scale Groundwater Resource Mapping and Vulnerability Assessment of MGB-IX Geosciences Division commenced on June 22 to July 11, 2019, in the Municipality of Kalawit. This is part of the groundwater resource study in the entire Zamboanga Peninsula which will cover 5 municipalities: Naga, Tampilisan, Kalawit, R.T. Lim, and Titay. This undertaking conducts well and spring inventory and aims to assess the vulnerability of groundwater resources that will likely be affected by global climate change and potential groundwater pollution. The assessment conducted is vital for the effective and efficient management of groundwater resources for sustainable development.

The program covers the entire municipality of Kalawit which is comprised of 14 barangays and will attempt to mapped-out all major water sources of each barangays. The municipality has a Level II-III water distribution system within the poblacion and nearby adjoining barangays. There are few dug wells within the municipality used by individual households for domestic purpose only while spring sources are being developed by the LGU to support the water supply of the municipality. The main sources of water in the area are derived from a spring and deep well.
Kalawit is located at the southern part of Mt. Dansalan and the geology of the area is largely associated with Dansalan Metamorphics that extends to Labason in the north. The southern part is underlain by the southwestern extent of the Tampilisan shear zone in central Zamboanga.

The output of this program is a hydrogeologic map or water availability map of Kalawit with accompanying report.

INITIAL FINDINGS

To date, a total of 72 groundwater occurrence were surveyed within the municipality comprising of shallow/dug wells, deep wells, and spring sources. Springs comprised the fifty-three percent of the inventoried sites while 43% are dug-wells and the remaining 4% are deep wells. The deep wells are located in Brgy. Poblacion and Brgy. Tugop.

Distribution of water sources inventoried in the Municipality of Kalawit.

The average depth of the shallow wells is 6.1 m below the ground. There were at least five inventoried wells with depths beyond 10m. The deepest well is at 13.5m located at Sitio Pulo Langan, Brgy. Poblacion. Two other wells in Poblacion have depths beyond 10m while Brgy. Gatas and Lower Pianon have one each at 11m and 12 m respectively.

Two deep wells (KAL-005 and KAL-026) are located in Brgy. Poblacion but only one is currently in operation. One deep well (KAL-065) located in Centro, Brgy. Tugop is reported to have murky water particularly during the rainy season and is not being utilized for drinking as stated by a barangay official during an interview.

Based on the LGU data obtained by the group, the highest spring occurrence (KAL-022) is at elevation 455 masl at Brgy. Fatima. Another spring occurrence at elevation >300masl is at Brgy. Daniel Maing (KAL-006) and Brgy. New Calamba (KAL-017). KAL-020 spring located at Brgy. Paraiso occurs at 119masl, one of the low-lying spring occurrence inventoried in the municipality.

The average discharge rate of the springs inventoried is at 0.4 liters/second. It was noted that the discharge rate of the springs is within the weak to moderate. This is likely related to the underlying geology of the municipality which is predominantly quart-mica-schist. The weakest discharge measured was 0.04 liters/second.

The municipality is predominantly underlain by metamorphic rocks particularly schist or is within a metamorphic terrain. Such type of geology is classified under a Hydrogeological Unit Type III-B. In this type, the local groundwater-regions underlain is underlain by impermeable rocks and is generally lacks or without significant groundwater except in cases where residuum, sufficiently leached area, and along the fractured zone. Based on the recent inventory and study, the team initially concluded that the eastern and north-eastern portion of the municipality.

GEORESISTIVITY

A Vertical Electrical Sounding (VES) geophysical survey method was employed in selected sites within the municipality to determine potential water-bearing layers and correlate the inventoried shallow well depths and existing well data information. In this study, 6 VES survey lines were carried out as part of the program in addition to water sampling and well inventory (Table 01). VES method is more appropriate for groundwater investigation at various geological conditions to access the sub-surface geoelectrical layers (Lashkaripour GD, et. al, 2005). Deduced apparent resistivity obtained from the survey are plotted to define the resistivity and thickness of possible water-bearing units (Lashkaripour GR, 2003). A Syscal Pro-Iris Instrument was employed in this geophysical survey and IPI2win software was utilized for data interpretation.

Details of the Georesistivity Survey Points (VES) in the Municipality of Kalawit.

LOCATION

Location Map of the Municipality of Kalawit, Zamboanga del Norte underlain by SRTM image.
Inventoried groundwater sources in the Municipality of Kalawit

WELL AND SPRING INVENTORY

This section discusses the water sources in selected barangays of the municipality particularly the main potable water source.

Palalian

The main source of water is a spring (with 2 to 3 sources) collected in one intake box prior to being collected in a reservoir. The springs are located in Purok Nangka. The water system supplies for Purok Kasoy, Lubi, and Mangga.

A water sample is collected for laboratory analysis. The water will be analyzed for sulfate, phosphate, iron, total suspended solids, and total hardness.

KAL-42, one of the potable water source in the barangay. A water sample for laboratory analysis was taken in this site.

Botong

The barangay is utilizing 3 springs for its main source which is at the midslope of a ridge that borders Brgy. Botong and Concepcion. Gravity method conveyed the water from the source to an existing reservoir prior to being distributed to a level-2 water system.
There are few scattered localized springs developed in the area for domestic purpose and utilized by the residents around.

KAL-046, a spring developed in the barangay utilized by the residents adajcent to the area for domestic use

Fatima

The main source of water is located in Purok 2, on the same prominent ridge that is underlain by metamorphic rocks. The water system is developed under a XAES Project (Xavier Agricultural Extension Service Foundation Inc.) with a Level-III water distribution. The water system supplies water to Purok 1, Purok 3, Purok 5 and Purok 6.

KAL-056, a small spring located on a gully. A least three residential houses utilized this spring for domestic purpose.

Pianon

Separated into two Sitio, Upper, and Lower Pianon, this barangay relies heavily on spring water as the main source of potable water. Upper Pianon has 1 spring source while 2 spring sources support Lower Pianon. XAES project developed the water system in the barangay in 1995 where water is being conveyed via the gravity method and stored in a reservoir close to the barangay center.

KAL-051, a shallow well located on the nprthern border of Labason and Kalawit. This newly built well is intercepted weathered metamorphic rocks.

San Jose

The main water source originates in Brgy. Fatima and utilized a gravity method to transport the water from the source to a reservoir located in the barangay. Breakage of the pipes is often a problem of the barangay due to its length and on certain circumstances, the pipes are deliberately cut. One of the barnagays with a very limited main water source.

KAL-053, A very old spring source where water percolates on the fractures of a quartz-schist. Discharge appears to be very weak but the well does not dry up during the dry season.

Concepcion

A spring located in Purok 3 and along the boundary of Brgy. Botong is the main source of potable water in the barangay. The water system is already a Level-III. Water from the source is carried only by gravity method into a reservoir. For now only Purok 3 is being serviced by the water system while the rest of the barangay heavily relies on private dug wells or nearby springs.

KAL-069, multiple spring occurrence in Brgy. Concepcion. Here, the team is guided by the barangay officials after conducting an interview for anecdotal accounts.

Tugop

Two main water sources support the barangay which are located on the rubber tree plantation (KAL-59 and KAL-060). Based on the outcropping metamorphic rocks, groundwater flows on the fractures. A deep well adjacent in the barangay Elementary school at 120 ft is only utilized for domestic purpose due to its murky appearance.

KAL-013, water sampling in a spring located in BLOCK 17. The spring is being developed for potable water and is situated on the foot hill inside a rubber plantation.

Gatas

The main potable water source is groundwater springs originating from Mt. Gampoy located east of the barangay. The reported discharge rate of the springs are 0.2Lps and 0.8 Lps for KAL-007 and KAL-008 respectively. The spring source supplies water in six puroks of the barangay except in Purok 1, where a barangay managed water system is present.
Several dug wells are present around the barangay as the main source was only operated a few years back. Shallow wells are generally for private used and are utilized generally for domestic purpose.

KAL-071, one of the several shallow wells present in the residential area of the barangay.

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