ESTIMATION, REALITY AND TREND OF GROUNDWATER NITRATE CONCENTRATION UNDER UNSEWERED AREA OF YOGYAKARTA CITY – INDONESIA

In the last two decades, urbanization has transformed Yogyakarta City expanding beyond its administrative area with about one million inhabitants. The City sited on shallow unconfined aquifer has rapidly changed without appropriate access to sanitation and piped water supply. Until now, only 9% of the urban population is served by sewers system and less than 30% of urban population have access to clean water which supplied by the local public water-work. Most of the urban population depend on shallow groundwater for much of their water supply. Regards to the massive used of on-site sanitation systems in the city, contamination of nitrate in shallow groundwater is predicted to occur and surveys of domestic dug wells have revealed a widespread nitrate contamination of the groundwater. Comparison of groundwater nitrate and chloride concentration from several old data and the latest data shows clearly an evidence of the increasing of nitrate concentration and nitrate leaching in the shallow groundwater under Yogyakarta City overtime. Considering the trend, it is no doubt that most of nitrate concentration under urbanized area in the Yogyakarta City will be greater than 50 mg/L in the next several years, if appropriate management action to deal with the on-site sanitation system is not conducted

Evolution of groundwater chemistry on shallow aquifer of Yogyakarta City urban area

Since 1980s, accelerated by urbanization, Yogyakarta City was shifting to many directions defined by main road networks and service centres. Urbanization has transformed rural dwellings to become urban settlements and generated urban agglomeration area. Until now, new business centres, education centres and tourism centres are growing hand in hand with new settlements (formal or informal) without proper provision of water supply and sanitation system. This condition increase the possibility of groundwater contamination from urban wastewater and a change of major chemistry of groundwater as shallow unconfined aquifer is lying under Yogyakarta City. To prove the evolution of groundwater chemistry, old data taken on 1980s were comparing with the recent groundwater chemistry data. The evaluation shows that nitrate content of groundwater in 1980s was a minor anion, but nowadays become a major anion, especially in the shallow groundwater in the centre of Yogyakarta City. This evidence shows that there is an evolution of groundwater chemistry in shallow groundwater below Yogyakarta City due to contamination from un-proper on-site sanitation system. Keywords: Urbanization, Yogyakarta city, rural dwellings, settlements, agglomeration, contamination, groundwate

Integrated Water Resources Management In Merapi Yogyakarta Basin

Dalam kerangka sumber daya air, cekungan airtanah Merapi Yogyakarta menghadapi banyak permasalahan degradasi sumber daya air berkaitan dengan tidak terintegrasinya pengelolaan sumber daya air, perubahan lahan yang sangat cepat di daerah resapan air dan peningkatan pemanfaatan airtanah akibat bertambahnya jumlah penduduk dan kegiatan-kegiatan perekonomian di wilayah ini. Berdasarkan permasalahan tersebut empat tahapan penelitian dilakukan dalam rangka penyusunan rencana pengelolaan terpadu sumber daya air yaitu (1) Koleksi dan organisasi data sumber daya air secara terpadu di dalam suatu sistem informasi, (2) perhitungan sumber daya air dan analisa kesetimbangan air, (3) analisa dan evaluasi penggunaan air serta pengaruhnya terhadap degragasi sumber daya air dan (4) pemodelan Watershed dan airtanah di cekungan airtanah Merapi Yogyakarta untuk mengetahui efek perubahan lahan terhadap volume resapan air dan volume airtanah . Hasil penelitian ini menunjukkan bahwa, pemanfaatan air untuk kepentingan di luar sektor pertanian berasal dari sumber daya airtanah dan untuk kepentingan sektor pertanian lebih dari 97% berasal dari sumber air permukaan, perhitungan sumber daya air menunjukkan bahwa secara umum volume airtanah dan air permukaan di wilayah ini masih mencukupi untuk memenuhi kebutuhan air walaupun secara lokal beberapa area tidak dapat memenuhi kebutuhan, degradasi sumber daya air lebih mengarah pada kualitas air yang semakin buruk sedangkan degradasi kuantitas air hanya terjadi pada beberapa lokasi yang bersifat lokal akibat tingginya eksploitasi dan efek impermeabilisasi pada sumber daya airtanah dan musim kemarau pada sumber air permukaan. Akhirnya dalam rangka pengelolaan yang berkelanjutan usulan pengelolaan, sumber daya air difokuskan untuk pelaksanaan conjuctive used antara airtanah dan air permukaan, pembagian zona-zona pengelolaan airtanah gelolaan dan zona perlindungan daerah resapan air

The Effectiveness of Wenner-Schlumberger and Dipole-dipole Array of 2D Geoelectrical Survey to Detect The Occurring of Groundwater in the Gunung Kidul Karst Aquifer System, Yogyakarta, Indonesia

Until today, geoelectrical survey is the most effective method for groundwater exploration. 2D method or known as horizontal profiling is now the most appropriate method in the geoelectrical survey compare to vertical electrical sounding method. The 2D method of Wenner-Schlumberger and Dipole-dipole configuration proved to be very effective to locate conventional aquifer occurrence on volcanic terrain or sedimentary terrain. Karst aquifer system is an unconventional aquifer and acts very differ in contrast with the conventional sedimentary aquifer. Heterogeneity and discontinuity of limestones in karst terrain will reveal a wide variety of resistivities, hence it is difficult to interpret. This research has important objective to define the effectiveness of the Wenner-Schlumberger and Dipole-dipole configuration in the 2D geoelectrical survey to explore groundwater in the karst area. Field observation of geology and 2D geoelectrical survey were conducted in underground river of Kali Suci Area, Gunung Kidul. In Kali Suci where an endokarst cave was occured on the surface, line survey was placed in the top of the cave and across the geometry of the cave. Measured stratigraphy in the wall of the cave found four types of limestone which consist of packstone, wackestone, grainstone and crystalline limestone. The Wenner-Schlumberger and Dipole-dipole method can detect differentiation of limestone types and also the exposed underground river successfully. However, compared to Wenner-Schlumberger array, Dipole-dipole array reveals less vertical accuration.. Therefore, on this research, the best method to detect water saturated zone or gourndwater in the karst system is the Wenner-Schlumberger method

Assessment of Groundwater Vulnerability and Total Organic Carbon in the Shallow Groundwater of Wonosari City, Gunung Kidul, Yogyakarta, Indonesia

Wonosari city is the capital of Gunung Kidul regency of Yogyakarta Special Province. The city is located in the karst plateau overlaying a succesion of limestone lithologies. The groundwater on this city is shallow and people used this groundwater as their daily water supply. This study aims to determine the intrinsic groundwater vulnerability and to identify the TOC level in groundwater also to investigate the relationship between groundwater vulnerability and TOC levels in the groundwater. Field observation was conducted on 40 groundwater occurrences (dug wells, bore wells and springs) to investigate the aquifer types, overlying lithology and depth to groundwater. At the same time, 16 groundwater samples were taken from the dug wells and analyse for the TOC content. Secondary data was also collected from previous researches especially the information of sub-surface lithology. Groundwater vulnerability was evaluate by using GOD method and correlation between groundwater vulnerability and TOC in groundwater was analyzed spatially and statistically by using map pverlaying, linear regression and Spearman’s rho test, respectively. The results showed that the groundwater vulnerability in the city is dominated by extreme and high vulnerability, covers about 84 % of study area. The TOC level in the groundwater ranges between  4.532 mg/L to 6.849 mg/L which showing a process of pollution loading may occur. Linear regression and Spearman’s rho value show that the TOC levels and  groundwater vulnerability has a moderate positive correlation with r2 value of about 0.324 for linear regression. Despite the moderate correlation, the research prove that the groundwater vulnerability map reveals on this study is good enough to represent the ability of natural condition in protecting the groundwater quality

COASTAL AQUIFER GROUNDWATER MODELING IN THE SOUTHERN PART OF YOGYAKARTA AREA, INDONESIA

Parangtritis beach, located in a coastal aquifer at the southern part of Yogyakarta Province, Indonesia is bounded by the Indian Ocean at the South, Opak River at the West, and Tertiary Limestone Rock to the East. Local land-use is predominantly agriculture, rice fields and settlements and the population is estimated to be 9,386 persons as per the 2012 census. The total surface area is estimated at 9.46 km2. The aims of this research were to understand the system of groundwater and to assess and predict saltwater intrusion by conducting a numerical groundwater model. Hydrological and hydrogeological data were collected directly from the field and from previous work for input into the model. The model simulates an unconfined aquifer system where the aquifer thickness varies from 30-40 meters. The material of the aquifer consists of sand varying from fine to coarse grain size and fine gravel with hydraulic conductivity values of 8.974 × 10−4, 1.794 × 10−3, and 1.337 × 10−3 m/s at the northern, central, and southern part of the research area, respectively. The maximum length of the saltwater interface was estimated at about 205.1 m laterally and 40 m vertically relative to the location of the groundwater table around 1m above sea level. Direction of groundwater flow is from north to south. Groundwater table elevation equals 5 m at the north and 0 m at the south with a hydraulic gradient estimated at about 2.45 × 10−3. As a result of a steady-state simulation as well as two cases of prediction for five and ten years in the future, it is determined that that the salinity of the surrounding environment is not potentially adverse to the groundwater quality in the study area. This is in part due to low population in this area and abundant groundwater resources, as well as the results of the groundwater model. Keywords: Coastal aquifer, numerical groundwater model, conceptual model, observed head

Removal Of Copper From Water Using Columns Experiment Of Lignite, Shale, And Ironsand

Experimental studies using column testing of lignite, shale, and ironsand in copper solution were carried out to determine the adsorption capacity of lignite, shale, and ironsand in remediation of water contaminated with copper. Lignite, shale, and ironsand were analyzed using XRD, SEM/EDX, and XRF. The treatment process by column adsorption was carried out over a period of 24 hours at a stable velocity of 0.005ml/s. After treatment, the remaining copper in the solution was recorded, thus allowing the adsorption capacity of lignite, shale, and ironsand to be calculated. The results revealed that when the solution was treated by lignite and shale there was a good degree of copper removal, while the ironsand had very poor degree of copper removal. The best material for copper removal was lignite with 25-mesh grain size. Pyrite, graphite, calcite, and illite were found in lignite and smectite, calcite, pyrite, hematite, and illite were found in shale. These materials were also shown to contain an abundance of high-valence elements in Al2O3, SiO2, and Fe3O4 which contributes to additional adsorption capacity. CAC values for lignite and shale reached nearly to 100%, suggesting that lignite and shale have a high adsorption capacity. In contrast, ironsand, which has mostly sand minerals with little clay and organic content, caused the pollutant to move rapidly to the water table, reducing the adsorption potential. CAC values treated by ironsand were shown to be negative which showed an increasing of Cu2+ in natural ironsand into solution. Keywords: Copper, ironsand, shale, lignite, column experimen

The Quality and Distribution of Andesite Rock for Construction Materials in Kokap and Temon District, Kulon Progo Regency, Yogyakarta–Indonesia

The construction projects that are currently being carried out in Kulon Progo Regency, Yogyakarta Special Province, Indonesia, started on 2018, are large-scale projects. The projects include the construction of airports, seaports, industrial estates, southern crossing lanes and the construction of Menoreh lanes. The large-scale projects require a very large supply of andesite rocks for material construction. In Kulon Progo Regency itself, there is a huge potential of andesite rock relate to two geological formations (Kebo Butak and Andesite Intrusion) exist in the region, which is found mostly in Kokap District and partly in Temon District. One parameter that determines the quality of andesite rock is their compressive strength. Due to weathering, not all of the andesite in both formation can be classified as good quality rocks. According to Indonesian Standard, theminimum compressive strength of natural stone for stakes and curbstone is 500 kg/cm2 , for lightweight building foundation is 800 kg/cm2 , for medium building foundations is 1000 kg/cm 2and for heavy building foundations is 1500 kg/cm 2 . Based on this background, this paper have objectives to know the quality of andesite rock exist in the research area and to determine the zonation of good quality andesite rock for building and road materials in the research area. Field observation were conducted to map the occurrence of andesite rock. Totally 68 rock samples were collected during field observation and tested by point load test method to know its compressive strength value. The distribution of good quality rock in the research area were determine based on spatial analysis procedure in geographical information system. Results show that andesite rocks found in research area have a compressive strength ranging from 167.12 kg/cm 2 to 2783.37 kg/cm 2 . From 53 samples taken from igneous rock intrusion, it showed that 7.55 % had low quality, 13.21 % had medium quality, 30.19 % had good quality and 49.06 % had very good quality. From the 16 samples taken from the Kebobutak Formation, it showed that 12.50 % had low quality, 18.75 % had good quality and 67.75 % had very good quality. The final map of rock quality zonation reveals 28.92 % of research area classify as low quality, 2.52 % medium quality, 37.68 % good quality and 30.88 % very good quality. It can be concluded that almost 70 % of andesite in the Kokap and Temon District can be used for the running large scale projects

Groundwater Flow Modeling in the Malioboro, Yogyakarta, Indonesia

Malioboro is a famous tourism area in Yogyakarta City, in which there aremany hotels and increases every years and this follows by the increasing needs of fresh water taken from underlying groundwater. The decreasing of groundwater table become a great issue on this area, therefore the objective of the research is to predict groundwater table change in the next 10 years due to increase abstraction of groundwater. To answer the mentioned objectives, field observation of dug wells and collection of secondary data of log bores also calculation of recharge and water abstraction are used to understand and build the conceptual model of local groundwater system. The prediction is done by conducting simulation on a numerical groundwater model by using MODFLOW. The local groundwater system consists of two aquifer layers; upper aquifer and lower aquifer which separated incompletely by clay layer. Simulation is conducting by distributing the groundwater pumping for domestic and non-domestic utilization by dug wells in the upper aquifer, whereas deep wells non-domestic utilization are applied only in the lower aquifer. Simulations are conducted twice for the recent day and the next ten years predictionof groundwater abstraction. In the case of groundwater abstraction in the next tenyears, dug wells abstraction and deep wells pumping are setting to 4727 m3/day and 1648 m3/day, respectively. The groundwater pumping rates is representing increase of groundwater withdrawal of users in the range only between 0.2–1.2 % per year compare to the recent condition. The simulation reveals change occur on groundwater table depth and pattern. In average, the groundwater table will decrease of about 0.25 meter

CHEMICAL COMPOSITION AND HYDRAULIC CONNECTIVITY OF SPRINGS IN THE SOUTHERN SLOPE OF MERAPI VOLCANO

Springs are easily found in the southern slope of Merapi volcano, Sleman Regency, Yogyakarta Special Province, Indonesia. Springs origins on this location are commonly related to the existing of Merapi Aquifer System, but importance question of all these springs are hydraulic connectivity among them. In response to the issue, the objective of this research is to determine hydraulic connectivity of springs based on their chemical composition. To answer the objectives, measurement of spring discharge and physicochemical properties of spring’s water and sampling of selected spring’s water were conducted on this research in the study area. Water chemistry composition was classify by Kurlov formula and displayed by Fingerprint diagram and Composition diagram. Results show that the chemical compositions of most all spring samples are almost similar and does not significantly different for most properties from upstream to downstream, which are Na–Ca–HCO3 water, only one spring of Umbul Jatiningsih spring had different chemical composition of Ca–Na–Mg– HCO3 water. Based on the Fingerprint diagram and Composition diagram evaluation, the spring’s water can be differentiated into three groups. Group 1 consists of ten springs which have similar chemical composition of Na–Ca–HCO3 and with electrical conductivity ranges between 150 to 200 mS/cm. Group 2 consists only one spring “Umbul Pajangan” which contain similar chemical composition to Group 1 but has significantly higher ions concentration (EC value about 400 mS/cm) and Group 3 consists also only one spring “Umbul Jatiningsih” which has significantly different ionic composition with Group 1 and 2. Regarding on this condition, it can be concluded that Group 1 spring is hydraulically connected and relate to the shallow aquifer system of Merapi Aquifer System. In other side, water of spring “Umbul Pajangan”possibly comes from deeper aquifer system of Merapi Aquifer System and this argument is supported by the spring discharge evaluation. Finally, spring “Umbul Jatiningsih” is originate mainly from different aquifer system of porous limestone aquifer. Keywords: Merapi aquifer system, spring, chemical composition, geological conditio