E-ISSN: 2579-5511/ P-ISSN: 2579-6097 doi https://doi.org/10.20886/jppdas.2020.4.2.187-200 ASSESSMENT OF GROUNDWATER QUALITY FOR IRRIGATION AT MALAMAWI ISLAND, BASILAN, PHILIPPINES Alejandro A. Jalil1, Roger A. Luyun, Jr2, Aurelio A. Delos Reyes, Jr2.,and Victorino A. Bato3, 1College of Agriculture and Fisheries, Basilan State College, Isabela City, Basilan, Philippines 2Land and water Res. Div., Inst. of Ag. Eng’g, College of Engineering and Agro-industrial Technology, University of the Philippines, Los Banos, Philippines 3Department of Soil Science, College of Agriculture, UPLB, Philippines Email : [email protected] Submitted: 22 February 2020; Revised: 26 October 2020 Accepted: 14 December 2020 ABSTRACT The assessment of groundwater quality for agricultural purposes was conducted in Malamawi Island, Isabela City, Basilan. Groundwater quality wasevaluated based on the FAO irrigation quality standards (1994)which include salinity and alkalinity, sodium, magnesium, bicarbonate hazards and chloride hazards. Spatial delineation of groundwater quality parameters was carried out using QGIS software. Results revealed that the use of groundwater from two separate sampling wells (SW4 and SW6) in Lukbuton area require slight to moderate restrictionbased on the parameters of electrical conductivity and magnesium hazard. This means that its groundwater can still be safe for irrigation but with little salinity hazard on sensitive crops.Also, the chloride concentration in SW4 indicates that groundwater was slightly poor in quality but generally suitasble for irrigation while in SW6, the calcium concentration was considered unsuitable for irrigation. In the same way, the sampling wells 1 and 3 in Santa Barbara and Lukbuton were considered unsafe and unsuitable for irrigation in terms of magnesium hazard. Also, the calcium content of groundwater in some part of the island was considered unsuitable for irrigating high-value crops. Therefore, this study suggests that some management is needed in the northeastern part of Lukbuton because of its poor ground water quality for irrigation in terms of salinity. Keywords: Malamawi, Basilan, irrigation, shallow well. ABSTRAK Penilaian kualitas air tanah untuk keperluan pertanian dilakukan di Pulau Malamawi, Kota Isabela, Basilan. Kualitas air tanah dievaluasi berdasarkan kesesuaian untuk irigasi sesuai standar kualitas irigasi FAO meliputi salinitas dan alkalinitas, serta bahaya natrium, magnesium, bikarbonat dan klorida. Delineasi spasial dari parameter kualitas air tanah dilakukan dengan menggunakan perangkat lunak QGIS. Hasil penelitian menunjukkan bahwa penggunaan airtanah dari dua sumur sampel terpisah (SW4 dan SW6) di kawasan Lukbuton memerlukan pembatasan ringan hingga sedang berdasarkan parameter @2020 JPPDAS All rights reserved. Open access under CC BY-NC-SA license. 187 Assessment Of Groundwater …………(Alejandro A. Jalil, Roger A. Luyun, Jr, Aurelio A. Delos Reyes, Jr., and Victorino A. Bato) konduktivitas listrik dan bahaya magnesium. Hal ini menunjukkan air tanah masih aman untuk irigasi walaupundengan sedikit bahaya salinitas untuk tanaman yang sensitif. Selain itu, konsentrasi klorida di SW4 menunjukkan bahwa kualitas airtanah agak buruk walaupun umumnya cocok untuk irigasi sedangkan di SW6, konsentrasi kalsium dianggap tidak sesuai untuk irigasi. Dengan cara yang sama, pengambilan sampel sumur 1 dan 3 di Santa Barbara dan Lukbuton dianggap tidak aman dan tidak cocok untuk irigasi dalam hal bahaya magnesium. Selain itu, kandungan kalsium air tanah di beberapa bagian pulau dianggap tidak sesuai untuk mengairi tanaman bernilai ekonomi tinggi. Oleh karena itu, studi ini menyarankan bahwa perlu dilakukan pengelolaan di bagian timur laut Lukbuton karena kualitas air tanah yang buruk untuk irigasi dari segi salinitas. Kata kunci: Malamawi, Basilan, irigasi, sumur dangkal I. INTRODUCTION pH, making it inimical for plant growth.Bicarbonates in the irrigation Groundwater qualityis essential for water has become a serious concern human life and inherent for economic because it increases the pH from 7.4 to vitality. It is also one of the most crucial 9.3 (ibid.). According to Alobaidy et al. factors for groundwater irrigation (Jang et (2010), a significant factor that escalates al., 2012; Jang et al., 2019). However, water pH to 8.0 and beyond is due to the during the hydrological cycle, metals and presence of carbonates. This significant other impurities were introduced in the amount in the irrigation water can directly water bodies through anthropogenic harm some plant species. Therefore, the activities such as the use of agrochemicals poor water quality can adversely affect (pesticides and fertilizers), coal plant growth regardless of its quantity combustion, and other low-quality fuel in (Alobaidy et al., 2010). brick kilns and other industries, untreated Because of that, there is a need to industrial effluents discharge, and the ascertain the groundwater quality before improper disposal of municipal solid it can be used for irrigation purposes to wastes (Nawab et al., 2018;Naseh et al., ensure optimum levels of plant growth 2018;Khanoranga & Khalid, 2019). (Mitra et al., 2007).Part of this is to These activities may affect the quality understand the groundwater of groundwater for irrigation. Highly characteristics through the monitoring contaminated irrigation water can cause and assessment of water’s quality apt for changes in soil permeability, soil pH, soil drinking, agricultural, and industrial uses structure and nutrient uptake by plants (Adimalla et al., 2019; Kuldip-Singh et al., (A. B. Iqbal et al., 2020). The excessive 2011; Adimalla et al., 2020). It is also sodium dissolution in irrigation water can important to determine the amount and lead to the soil’s higher Sodium kind of salt present in the water because Adsorption Ratio (SAR)making it less poor water quality tends to cause various suitable for irrigation. Also, the presence cropping problems. The suitability of of bicarbonates (HCO3) and carbonates - groundwater irrigation depends on the (CO3 ) in the water tend to increase the 188 @2020 JPPDAS All rights reserved. Open access under CC BY-NC-SA license. JurnalPenelitianPengelolaan DaerahAliranSungai E-ISSN: 2579-5511/ P-ISSN: 2579-6097 (Journal of Watershed Management Research) Vol. 4 No.2, Oktober2020 :187-200 salinity, conductivity, and hardness of II. MATERIALS AND METHODS water ((Singh & Khare, 2008). Among the A. The Study Area major cations to be monitored include Malamawi Island (Figure 1) is about calcium, magnesium, and sodium which 300 m from the main island of Basilan. It also influence the suitability of has a total delineated area of about 947 groundwater for irrigation. These cations Has. The island consists of seven different can be toxic to plants, affect soil villages which islocated between 6042’46” properties and management practices, N and 6044’45” N latitudes, 121056’24” E but can also be beneficial to crop and 121058’23” E longitudes. The general production at desirable concentrations elevations ranged from 5 m to 103 m (FAO, 1994). above sea level while slopes ranged from In Malamawi Island in Basilan, all crops 3% to 30%. The island has a current grown are rain-fed. However, there is still population of 13,859 with most houses a need to determine whether the built along the shoreline. groundwater quality is suited for The island is dominated by agricultural irrigation. There is also a possibility to activities. Most areas are planted with recommend an installation of artificial coconut, mango, and citrus trees (Figure irrigation system to intensify crop 2). The hilly portions were regularly production if the groundwater quality is planted with small-scale root crops and suitable for irrigation. Therefore, this vegetables. Almost all of the entirearea study was conducted to assess the quality that consists of Bulawan clay loamare of shallow ground water in six sampling cultivated with rice, corn, and coconut. wells in the island to determine its The island has a type IIIclimate suitability for agricultural purposes based classification, where the seasons are not on the standard water quality guidelines very pronounced, relatively dry from of Food and Agriculture Organization November to April, and wet during the (1994), and spatially mapped each rest of the year (Bangsamoro groundwater quality parameter through Development Agency, 2016). The annual interpolation using QGIS to present its mean temperature and precipitation is concentration in the entire Island. The 26.6oC and 1,100 mm respectively results of the study may serve as baseline (Bangsamoro Development Agency, information particularly the current 2016). measured parameter concentrations in Malamawi Island, Basilan. @2020 JPPDAS All rights reserved. Open access under CC BY-NC-SA license. 189 Assessment Of Groundwater …………(Alejandro A. Jalil, Roger A. Luyun, Jr, Aurelio A. Delos Reyes, Jr., and Victorino A. Bato) b a Figure 1. Location maps, a. Study area (Source: Google Earth, 2015) and , b. Sampling and existing Shallow wells in Malamawi Island, Isabela City, Basilan, Zamboanga Peninsula,Philippines Figure 2. Land Use Classification Mapof Malamawi Island, Basilan, Zamboanga Peninsula, Philippines 190 @2020 JPPDAS All rights reserved. Open access under CC BY-NC-SA license. JurnalPenelitianPengelolaan DaerahAliranSungai E-ISSN: 2579-5511/ P-ISSN: 2579-6097 (Journal of Watershed Management Research) Vol. 4 No.2, Oktober2020 :187-200 B. Indicators of Water Quality for groundwater, the sampling