No abstract

Water tracing was conducted at Karangbolong Karst as a rapid assessment of the Kalisirah spring hydrological characteristics. This study was conducted to determine the movement of underground flow and the estimation of the Catchment Area using the Todd Nomogram and field observations. The results of flow tracing tests conducted in Pocung Cave indicate that there is underground river network connectivity between Pocung Cave, Jeblosan Sinkhole and Kalisirah Springs. Based on topographic survey and flow tracing test, the calculation of the estimated area of the Kalisirah catchment area is 180 Ha. The results were also validate using other parameters, namely flowrate and rainfall in the research location using Todd Nomogram. The estimated area of the Kalisirah catchment area with the Todd Nomogram is 189.2 Ha. The calculation of the estimated area of Kalisirah catchment area based on topographic survey and water tracing is relevant with the estimated area with Todd Nomogram. Groundwater tracing investigation can be used to determine karst spring catchment area, as a preliminary study to understanding the karst hydrology.

Sand dune in Parangtritis Village has a speciality of being formed in humid climates (tropical). The initiation of Barchan Sand Dune as a new tourism based on eco-tourism has to consider many aspects to maintain sustainability of sand dune. It needs some information on economic valuation to determine the capacity of tourism objects as a consideration of sand dune's sustainability. The purpose of this research is to know the projection of Barchan sand tourism's feasibility until 2045. The research method is the economic valuation approach by calculating Nett Present Value (NPV) as the analysis (cost) and the benefit earned by Barchan Sand Dune Tourism. The method of economic valuation is chosen because it is able to convert ecosystem services into currency value (IDR) so that it can be a valid comparator. The hypothesis in this study states that the feasibility of Barchan Sand Dune Tourism will increase until certain year, but the increased feasibility will cease in a certain year and decrease in the following year. The results are obtained based on the calculation of Nett Present Value (NPV), it shows positive value so that Barchan Sand Dune Tourism is feasible to continue until 2045 with estimated profit reached IDR648,000,000. The calculation results show a decrease in the level of tourism efficiency in 2017. The level of efficiency can be increased again through management optimization based on the characteristics of the tour, which are something to do, something to see and something to buy at Sand Dune Barchan.

Anjani underground river was one of the biggest water resource in Jonggrangan Karst. The objective of this research was to describe hydrochemical temporal variation which was expected to assist in defining the aquifer conditions that recharge Anjani underground river in more detail. Sampling was carried out for one year covering dry and wet seasons, as well as the flood events. The hydrochemical analysis was conducted based on dissolved major ion concentration and physicochemical properties. In addition, SIcalcite and log PCO2 were calculated to understand the temporal variation of aggressiveness on calcite mineral. The results showed that all water samples performed HCO3-Ca type. The chemical constituent in water varied temporally which showed high during dry season and decreased during wet season. The high chemical constituent during dry season was caused by the domination of slow-flow (diffuse) so the water had a longer residence time in aquifer, allowing water-rock interaction to be more intensive. Meanwhile, the low dissolved constituent during wet season was caused by input from quick-flow that changed water-rock interaction into dilution by precipitation process. Generally, all water samples was saturated with respect to calcite, except during flood events. One of the factors that affected this condition was CO2 supply from the allogenic river that allowed the dissolution process to be more intensive.

Karst aquifer flow can be divided into diffuse, fissure, and conduit. Diffuse (base) flow plays a role in maintaining the continuity of karst springs. This research was conducted in the Kiskendo underground river, Mudal spring, and Anjani underground river, which is located in the Jonggrangan karst area, to determine variations in the base flow proportion in the three locations. Water level and discharge data are collected for a year (March 2018-March 2019). The water level and discharge data pairs are then used to create a rating curve to obtain flow hydrographs during the study period. Several flood events are then chosen to calculate the baseflow recession constant. Separation of base flow is automatically carried out to determine the percentage of base flow during the study period. The results showed that all three locations had fluctuating hydrographs that followed the seasons, with many peaks of flood hydrographs occurred following rainfall events. This condition shows that all three locations have developed aquifers. Although this is the case, flows in the three locations tend to be dominated by base flow both during the dry and rainy seasons, which indicates the capacity of aquifers to store groundwater is still good. Besides, the results of the base flow separation show that the percentage increases during the dry season and decreases during the rainy season. The decrease in the percentage of base flow during the rainy season is due to the contribution of direct flow (fissure and conduit) to the karstic aquifer.