Pemetaan Zona Kerentanan Airtanah Pesisir Formasi Batugamping Terhadap Pencemaran Nitrat Di Kecamatan Sepulu Madura

Fomasi litologi akuifer batugamping mempunyai karakteristik media aliran berupa celah, rekahan, dan lorong pelarutan, sehingga memiliki potensi mengalirkan airtanah dengan kecepatan tinggi. Produktivitas yang tinggi ini mengakibatkan sumber pencemar di permukaan dapat dengan cepat meresap ke sistem akuifer dan bercampur dengan airtanah; kondisi inilah yang memicu kerentanan tinggi. Salah satu langkah pengelolaan airtanah pesisir adalah penentuan zona kerentanan airtanah terhadap pencemaran. Dengan demikian, tujuan penelitian ini adalah untuk mengetahui tingkat kerentanan airtanah pesisir terhadap pencemaran di formasi batugamping menggunakan metode COP dengan pendekatan intrinsik dan metode EPIK dengan pendekatan perkembangan karst. Hasil penilaian menggunakan kedua metode tersebut menunjukkan tingkat kerentanan rendah hingga sangat tinggi. Pemetaan metode COP menghasilkan dua kelas kerentanan: rendah (95% dari luas wilayah) dan sedang (4%), sedangkan metode EPIK menghasilkan zona indeks kerentanan yang lebih panjang dengan empat kelas kerentanan, yaitu rendah (1,23%), sedang (17,82%), tinggi (17,82%), dan sangat tinggi (21,65%). Dibandingkan dengan COP, EPIK menghasilkan kelas kerentanan yang lebih tinggi karena pengaruh koefisien pembobot pada formula penghitungannya. Hasil penilaian kerentanan divalidasi dengan indikator limbah domestik berupa senyawa nitrat (NO3). Uji laboratorium menunjukkan kandungan nitrat (NO3) airtanah yang bervariasi dari 0,12 mg/l (terendah) hingga 9,80 mg/l (tertinggi). Variasi ini masih berada di bawah baku mutu air minum tetapi di atas baku mutu air limbah domestik atau melebihi kadar nitrat di alam. Berdasarkan hasil validasi, zona kerentanan berkorelasi dengan kandungan nitrat (NO3). Pada zona kerentanan yang tinggi, ditemukan kadar nitrat yang tinggi pula.ABSTRACTA limestone aquifer is lithologically characterized by three flow media: fissures, fractures, and dissolution channels, thus creating the potential to drain groundwater at a high rate. This high productivity, however, means that the groundwater is highly vulnerable to pollution. If a pollutant source is present on the surface, it can quickly seep into and mix with the subsurface system. Among the widely proposed management strategies is groundwater vulnerability zoning. This study was intended to determine the degrees of coastal groundwater vulnerability to pollution in a limestone formation with two methods: COP intrinsic vulnerability) and EPIK (karst development-based vulnerability). The assessment results showed that the vulnerability produced with both methods varied from low to very high. In the mapping, COP produced two levels: low (95% of the total area) and medium (4%), while EPIK generated a longer vulnerability index zone with four levels: low (1.23%), medium (17.82%), high (17.82%), and very high (21.65%). Compared to COP, EPIK results in a higher vulnerability class due to the weighting values in its vulnerability assessment. The results were validated with a domestic waste indicator: the presence of nitrate (NO3). Laboratory tests showed NO3 concentrations in the range 0.12 of 9.80 mg/l. These figures are still below the quality standard for drinking water but above that of domestic wastes or exceeding the maximum NO3 content found in nature. The validation revealed that the vulnerability zone is correlated with NO3 levels: the higher the vulnerability class of the zone, the higher the nitrate content.

GIS-based MCDA for Gully Vulnerability Mapping Using AHP Techniques

This paper explores the potentiality of GIS-based Multi-Criteria Decision Analysis (MCDA) and Analytical Hierarchy Process (AHP) for gully vulnerability mapping. Multilayer information of basin characteristics, such as drainage density, Topographic Wetness Index (TWI), Stream Power Index (SPI), slope aspect and land use land cover (LULC), were used in this study to develop a Gully Vulnerability Index (GVI). A weighted approach was implemented on each criterion relative to their inferred influence on gully vulnerability and validated by determining the Consistency Ratio (CR). Findings show a varying magnitude of gully vulnerability across the study area. The low to medium gully vulnerability class was dominant covering a land area of 6557ha (21.25%), and mostly confined to developed areas. Still, it is noteworthy to observe that the severe gully vulnerability class covers a substantial land area of 5825ha (18.88%), which presents a great risk to infrastructural development and human settlements in the study area. The study has a model predictive capability with accuracy rate of 84.62%. The integration of the MCDA and AHP into GIS workflow is an effective approach critical to minimize the limitations associated with gully occurrence analysis, using a singular basin characteristic. The results obtained in the study will equally be important in determining gully risk zones, circumspect urban development, tracking and proper infrastructure construction plans for long-term gully disaster mitigation.

Land degradation vulnerability assessment based on land use changes and FAO suitability analysis in Jordan

The objective of this research was to investigate the pattern of land use change and its impact on land degradation in the Mediterranean regions of Jordan. Land use was interpreted using aerial photos and high-resolution satellite images and fieldwork carried out in 2018. Assessment of the degradation vulnerability degree was based on comparing the current land use with the potential suitability of the land by using FAO framework and spatial analysis techniques. The pattern of land use change from 1958 to 2018 showed that the area of rangeland and field crops declined by 16.1%, and 13.5% respectively; while the potential suitability for land utilization showed that 80% of the catchment is highly suitable for forest and rangeland in classes S<strong>₁</strong> and S<strong>₂</strong> respectively. The degree of vulnerability for land degradation under the current land use was assessed based on the erosion hazard, slope percent, and soil depth. The highest vulnerability class represents 10%, the medium vulnerability class covers 24%, the slightly moderate vulnerability class covers 31%, and the low vulnerability class consists of about 22% of the catchment area. In summary, the main constraints contributing to land degradation are improper land use by cultivation under high erosion hazard and slope degree followed by shallow soil depth.

Modeling the risk of groundwater contamination using modified DRASTIC and GIS in Amman-Zerqa Basin, Jordan

Amman-Zerqa Basin (AZB) is the second largest groundwater basin in Jordan with the highest abstraction rate, where more than 28% of total abstractions in Jordan come from this basin. In view of the extensive reliance on this basin, contamination of AZB groundwater became an alarming issue. This paper develops a Modified DRASTIC model by combining the generic DRASTIC model with land use activities and lineament density for the study area with a new model map that evaluates pollution potential of groundwater resources in AZB to various types of pollution. It involves the comparison of modified DRASTIC model that integrates nitrate loading along with other DRASTIC parameters. In addition, parameters to account for differences in land use and lineaments density were added to the DRASTIC model to reflect their influences on groundwater pollution potential. The DRASTIC model showed only 0.08% (3 km2) of the AZB is situated in the high vulnerability area and about 30% of the basin is located in the moderately vulnerable zone (mainly in central basin). After modifying the DRASTIC to account for lineament density, about 87% of the area was classified as having low pollution potential and no vulnerability class accounts for about 5.01% of the AZB area. The moderately susceptible zone covers 7.83% of the basin’s total area and the high vulnerability area constitutes 0.13%. The vulnerability map based on land use revealed that about 71% of the study area has low pollution potential and no vulnerability area accounts for about 0.55%, whereas moderate pollution potential zone covers an area of 28.35% and the high vulnerability class constitutes 0.11% of AZB. The final DRASTIC model which combined all DRASTIC models shows that slightly more than 89% of the study area falls under low pollution risk and about 6% is considered areas with no vulnerability. The moderate pollution risk potential covers an area of about 4% of AZB and the high vulnerability class constitutes 0.21% of the basin. The results also showed that an area of about 1761 km2 of bare soils is of low vulnerability, whereas about 28 km2 is moderately vulnerable. For agriculture and the urban sector, approximately 1472 km2 are located within the low vulnerability zone and about 144 km2 are moderately vulnerable, which together account for about 8% of the total agriculture and urban area. These areas are contaminated with human activities, particularly from the agriculture. Management of land use must be considered when changing human or agricultural activity patterns in the study area, to reduce groundwater vulnerability in the basin. The results also showed that the wells with the highest nitrate levels (81–107 mg/l) were located in high vulnerable areas and are attributed to leakage from old sewage water.

Considerations on the assessment of macroseismic intensity

Following a brief overview on the main characteristics of MCS (1930; the most employed in Italy), MSK (1981) and EMS (1992) macroseismic scales, considerations on their validity to underline the severity of damage on buildings are reported and discussed. Observations carried out on damage related to recent Italian earthquakes show that the seismic behaviour of buildings does not fit that provided by the scales, particularly with regard to the relationship <<vulnerability class vs. building type>>.