Ekosistem terumbu karang adalah ekosistem laut yang sangat rentan oleh kerusakan lingkungan. Terumbu karang di perairan Bilik, Taman Nasional Baluran merupakan contoh ekosistem terumbu karang yang mengalami ancaman kerusakan lingkungan akibat perubahan iklim dan aktivitas manusia. Salah satu metode yang dapat digunakan untuk memonitor kesehatan terumbu karang adalah dengan melihat kelimpahan megabentos dalam ekosistem terumbu karang. Oleh karena itu, penelitian ini memiliki tujuan untuk mengetahui kesehatan ekosistem terumbu karang dengan melihat kelimpahan megabentos di perairan Bilik, Taman Nasional Baluran. Metode yang digunakan dalam inventarisasi megabentos adalah dengan Benthos Belt Transect dan analisis video di Blok Sijile dan Blok Jeding di Perairan Bilik. Hasil pengamatan menunjukkan bahwa di Blok Sijile tidak ditemukan ekosistem terumbu karang dan megabentos. Sementara itu di Blok Jeding ditemukan ekosistem terumbu karang dengan megabentos berupa bulu babi dan bintang laut biru. Kelimpahan bulu babi di dan bintang laut biru adalah 0-0,14 individu/m2. Kondisi tersebut menunjukkan bahwa kesehatan ekosistem terumbu karang di Blok Jeding perairan Bilik Sijile masih baik, namun perlu mendapat perhatian khusus karena sebagian area terumbu karang mengalami pemutihan akibat aktivitas perikanan yang tidak ramah lingkungan.MEGABENTHOS ABUNDANCE AS CORAL HEALTH INDICATORS IN BILIK WATERS, BALURAN NATIONAL PARK, INDONESIA. Coral reef ecosystems are marine ecosystems that are prone to environmental damage. Coral reefs in Bilik waters, Baluran National Park, are examples of coral reef ecosystems that are threatened by environmental damage due to climate change and human activities. One of the methods for health monitoring of coral reefs is by looking at the abundance of megabenthos in coral reef ecosystems. Therefore, this study aims to determine the health of coral reef ecosystems by looking at the abundance of megabenthos in Bilik waters, Baluran National Park. We used Benthos Belt Transect and video analysis to identify the spatial distribution and number of megabenthos in Sijile Block and Jeding Block, Bilik waters. The results showed that in Sijile Block, there were no coral reef neither megabenthos ecosystems. Meanwhile, in Jeding Block, there was a coral reefs ecosystem with megabenthos in the form of sea urchins and blue starfish. The abundance of sea urchins and the blue sea star in Jeding Block was about 0-0.14 individual/m2. These conditions indicate that the health of the coral reef ecosystem in Jeding Block, Bilik waters was still in good condition, even though it still needs special attention related to coral bleaching as a consequence of fisheries activities that are not environmentally friendly.

The scarcity of water in most Yogyakarta grounds water basin is because of decreasing the groundwater recharge as the implication of the build-up area growing. One exception is in Upper Belik Watershed in which more than 95% covered as paved area. In order to reduce the runoff, the infiltration well must be applied. The artificial well design depends on the characteristics of impermeable layer that can be seen by its depth. So the analysist of impermeable layer depth is extremely important to be researched. Distribution of the impermeable layer can be interpreted using Geosonar. Therefore, the purpose of this research is to find the distribution of impermeable layers in Upper Belik Catchment. The primary data used systematic random sampling base on grid size 125x125 m. Spatial data analysis of the impermeable layer utilized to visualize the result of material type which consists of sand, little gravel, tuff, clay sands, sandy clay, and gravel in research location. Variation of impermeable layer depth divided into 5 classes which are: I (9-10 m); II (10-20 m); III (20-30 m); IV (30-40 m); and V (>40m). The composition of the impermeable layer material dominated by clay and tuff in Upper Belik watershed and located below the groundwater level.

Watershed management is important, especially to water management. River water pollution in the upstream has an impact on the water quality in the midstream and downstream. Boyong River is an upstream part of Code Watershed which has three dominant land uses. Land use activities in the Boyong River cause faecal pollution from animals or humans waste in river bodies. This can cause the presence of coliform bacteria in rivers, both Total Coliform (TC) and Fecal Coliform (FC). This study aims to determine the effect of land use on the number of TC and FC in the Boyong River. The study focused on three dominant land uses, mixed-use gardens, irrigated fields, and settlements. Sampling was carried out during the dry season and rainy season, using a purposive sampling method. Based on laboratory tests with the Most Probable Number (MPN) method, the number of TC ranged from <1,8 – 350.000 MPN/100mL and the number of FC ranged from <1,8 – 79.000 MPN/100mL. Third land use contributes to river pollution. Settlements have the highest number of TC and FC changing. During the rainy season, the number of TC and FC tends to be higher than during the dry season. Almost all sample points exceed the Boyong River allotment quality standard.

No abstract

Belik Watershed is one of a catchment which located in urbanized area of Yogyakarta. The upper stream part of this watershed have very important role as recharge area. However, vast land conversion occurrence in Sleman Regency threatened its function and cause several inundation case within the area. In other words, stream capacity unable to accommodate the surface runoff. This research intend to analyzed rainfall return period and compare rainfall intensity analysis methods to be implement in the research area. Furthermore, statistical analysis performed to carry out suitable method in the previous research aims. The comparison of rainfall intensity analysis in the short time series distance utilizes Talbot Method and Sherman Method. Rainfall data of short times series distance obtained from Automatic Water Rainfall (ARR). This Calculations of the standard deviatiornesearch analyse 2, 5, 10, 25 and 50 years of return period. Calculations of the standard deviation and error square mean root peak-weight (PWRMSE) determine to choose which method has a better result. The design of rainfall intensity result shown in the Intensity-Duration-Frequency (IDF) graph. Based on the calculation, the most appropriate method is the Sherman Method with standard deviation and PWRMSE for each return period in chronological order of 2 years (-0.27) (Z 3.52); 5 years (-0.67) (Z 3.83); 10 years (0.3) (Z 5.39); 25 years (0.6) (Z 7.56); and 50 years (-1.0) (Z 9.72).