Karst area is highly susceptible to changes to climate parameters. One of the parameters is rainfall variability. In addition to shaping the condition of water resources, rainfall in the Gunung Sewu karst area determines the nature of crop and livestock of the agriculture sectors―the local population's main economic activities, warranting the significance of the rainfall variability studies. Rainfall variability in karst areas also affects disaster conditions such as drought and floods. However, due to insufficient meteorological data in quality and quantity, there has been no rainfall variability studies conducted in this locality. The research intended to analyze rainfall variability in the Gunung Sewu karst area in 1979‒2013 by utilizing rainfall predictions from satellite images that many scholars had tested in different locations and recognized as having good quality. In the analysis, mean monthly rainfall was calculated, and the trends of annual rainfall and average rainfall intensity, dry and rainy seasons, the number of rainy days, and the effect of ENSO (El Niño Southern Oscillation) on rainfall were analyzed. The research data were 35 years of daily rainfall records derived from the National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR). The analysis results showed that the mean rainfall, number of rainy days, and rainfall intensity had an increasing trend. Also, El Niño quantitatively influenced the rain in the Gunung Kidul karst area.

Irrigation, a critical element in farming, can fulfill crop water needs and increase agricultural productivity during the dry season, provided that the two necessary factors are met, namely water supply and water quality. Water quality is a principal factor in assessing whether or not a water body is usable as a source of irrigation. Excess or lack of elements in irrigation water may affect irrigated crops and soil. For maximum harvests, studies scrutinizing the suitability of water supply for irrigation become necessary. Beton Spring has a large discharge, which the people of Ponjong District, Gunungkidul Regency, rely on for their irrigation and fish farming practices. Uniquely, this karst spring receives allogenic recharges from outside the karst area. This research was intended to assess the suitability of water quality of Beton Spring for temporal irrigation purposes by Sodium analysis (Na%), Sodium Adsorption Ratio (SAR), USSL, and Wilcox. The elements observed in the analysis were Ca2+, Na+, Mg2+, K+ and electrical conductivity. Based on the overall analysis results of the water quality series—Sodium analysis (the water samples were classified as Excellent), SAR (Excellent), USSL (moderate to good), and Wilcox (Excellent to Good), Beton Spring produces good-quality water that is suitable for irrigation.

The Pindul Cave Underground River is a source of water that is used for irrigation, fulfilling domestic needs, and also tourism. The source of water in the Pindul Cave Underground River comes from the surface river flow that enters the ponor (Allogenic Recharge) so that it affects the water quality in the Pindul Cave Underground River. The research was conducted with the aim of temporally analyzing the water quality in the Pindul Cave Underground River. River water samples were taken periodically for one year. Water quality was analyzed by comparing samples from laboratory and field tests with quality standards and hydrogeochemical analysis using triangle piper diagrams and rectangular piper diagrams. The results show that allogeneic affixes have an effect in the form of a relatively fast dilution process in the rainy season, thereby reducing the calcium value. This condition causes the water quality in the rainy season to be better than the dry season because the calcium level decreases and does not exceed the water quality standard. The results are corroborated by triangular and rectangular piper diagram analysis which shows that the water in the Pindul Cave Underground River is classified as calcium enrichment, unpolluted water.

This research was conducted in the Pindul underground river, a cave tubing tourism site in Gunungsewu Karst, Indonesia. The purpose of this study is to identify flood hydrograph parameters that can be used to characterise how karst aquifer release groundwater storage. The recording of water level fluctuations was carried out with the installation of HOBO U20L-02 (November 2020-August 2021). The discharge measurement was carried out 20 times to create a stage-discharge rating curve. Furthermore, eleven flood events were selected to calculate the recession constant of diffuse (Kb), fissure (Ki), conduit (Kc), time to peak (Tp), and time to baseflow (Tb). The results of the calculation of the hydrograph parameters show the number Kb=0.996, which indicates the slow release of groundwater storage supported by the Tb value = 20.72 hours (long enough). Compared with Kb and Tb values in other karst springs in Java, the Pindul underground river has a slightly slower than average releasing of groundwater storage, although its Tb value is shorter than the average for other karst springs. Meanwhile, based on the Kc value (0.429), the Pindul underground river is faster in releasing its conduit flow which is strengthened by a reasonably short Tp data (3.1 hours).

Economic development in Jakarta has been influencing physical and social characteristics of urban area significantly. For recent years, burgeoning population growth occurs as a result of urban development and contributes to the landuse dynamics in a certain area. Cengkareng, is one of the most developed urban areas in Jakarta and has been experiencing such population and landuse dynamics. Its strategic location has turned this area becomen densely-populated. Increasing population density increase land demand, shapes the settlement pattern, and changes the landuse of the area. A study conducted in Cengkareng District has been done to describe how the population density impacts the landuse features for landuse assessment. The method implemented in this study combines quantitative and qualitative to process statistics and satellite imagery to produce data of population density, landuse change, and settlement pattern of the studied area. The study resulted that Cengkareng has experienced such significant landuse change which is dominantly converted into settlement and offices due to rising of population density. Nucleated settlement pattern has taken more area regarding to increased land need over land supply. It becomes serious problem for Cengkareng such aa slum settlements, flood problems, and land subsidence.   Keywords: Landuse change; Population density; Settlement pattern