Lily Montarcih Limantara

This study evaluated the effects of combined vermicompost and nitrogen fertilisation on soil physical properties and the yield of mustard greens (Brassica juncea L.) cultivated under coastal dryland conditions in Jungutbatu Village, Nusa Lembongan, Bali, Indonesia. The experiment was conducted during a single growing season using a factorial randomised block design with six vermicompost rates (0–25 Mg∙ha−1) and four nitrogen levels (0–138 kg N∙ha−1), each replicated three times. Vermicompost was incorporated into the soil prior to planting, while nitrogen was applied as urea during crop growth. Plant growth parameters, biomass yield, and selected soil physical and chemical properties were assessed. The combined application of vermicompost and nitrogen significantly affected the plant height, leaf area index, and total biomass yield. The highest fresh (238.52 Mg∙ha−1) and oven-dried biomass (12.53 Mg∙ha−1) were obtained with 25 Mg∙ha−1 vermicompost combined with 138 kg N∙ha−1. Improvements in soil porosity and permeability, and reductions in bulk density, were also observed as accompanied by increases in soil organic carbon and total nitrogen. Regression analysis indicated predominantly linear responses of biomass yield to increasing fertiliser doses, suggesting additive rather than synergistic effects under the conditions of this study. These findings demonstrate the short-term potential of integrated organic and inorganic fertilisation to improve mustard productivity and soil physical quality in nutrient-poor coastal drylands. However, further multi-season and multi-site studies are required to evaluate the long-term soil effects, environmental risks, and the economic feasibility of high vermicompost application rates.

This study evaluates the effectiveness of telaga-based rainwater harvesting (RWH) systems in Tepus and Semanu Sub-districts of Gunungkidul, Yogyakarta, Indonesia, in supporting water availability throughout the dry season. The methods included field surveys of 40 telaga/embung1 (morphometric/depth measurements, inlet– catchment conditions, and operational status), descriptive statistical analysis, and estimation of water losses using the FAO-56 Penman–Monteith method (ETo), which was converted into open-water evaporation (Eo). Results show an average designed storage volume of 14,870 m3, while actual effective volume is only approx. 35% due to an average sedimentation rate of 48.25% (50% of telaga fall into the ≥51% sedimentation category). The theoretical rainwater- harvesting effectiveness is 20.85%, whereas actual effectiveness is 6.09% (actual range 0–33.8%; 37.5% of telaga have lost their function). At peak dry-season conditions, Eo ranges from approx. 5–7 mm per day (approx. 31–43 m3 per day for an average surface area of 6,138 m2). Accumulated evaporation over approximately 90 days is equivalent to approx. 2.76–3.87∙103 m3, or approx. 53–74% of the initial effective storage (approx. 5.20∙103 m3). Operationally, telaga retain their functional capacity for only ±2–3 months after the rainy season, rendering their supply insufficient to meet demand over the entire dry period.

This research aims to develop Horton infiltration for tropical peatland using an injection-well approach that relates soil moisture to the infiltration rate. The research was conducted in the peatland of Palangka Raya City – Sebangau District, Indonesia. Soil sampling was carried out to determine the depth of shallow peatland (50–100 cm) and medium peatland (100–200 cm) using an auger and ring samples. The methodology consisted of investigating a simple laboratory-scale injection-simulator model covering dimension, depth, number, and flow velocity, and then developing a Horton infiltration model for tropical peatland using an injection-well approach that relates soil moisture to the infiltration rate. The results show that the modified Horton infiltration analysis, with the addition of moisture in the simple injection-simulator tool, produces a very strong relationship between discharge and modified Horton infiltration, a very strong relationship between discharge and groundwater level, and a very strong relationship between modified Horton infiltration and groundwater level in medium-depth peatland deeper than one metre (>1 m). The modified Horton infiltration development model for tropical peatland is better than the original Horton infiltration model because peatland is porous and infiltration increases with increasing water volume and soil moisture. In addition, the injection well increases the infiltration-capacity system, whereas the original Horton model analyses only natural infiltration.

Cavitation in high-velocity spillways is a critical issue in modern hydraulic design, particularly in channels with downward concave vertical curvature, which are vulnerable to negative pressure and jet reattachment. This study aims to evaluate the influence of aerator position, using a deflector-groove type, on flow characteristics, pressure distribution, entrained air mass, and the cavitation index in a multi-slope spillway through CFD-based numerical simulation. Five aerator configurations, labeled A to E, were analyzed under a design discharge of 1,154.3 m³/s, using the SST k–ω turbulence model and mesh sizes ranging from 220 to 500 mm. Validation against physical data showed a high level of significance, with R² > 0.9, confirming the reliability of the numerical model used. The velocity distribution indicates that the aerator location significantly influences air-jet formation and air-cavity stability. The aerator positioned at the center of the concave section, Series A, produced the most stable flow pattern, controlled negative pressure, and an entrained air mass of 63 kg/s. In addition, the cavitation index value for Series A showed an average increase of up to 20% compared with the other configurations, indicating the effectiveness of this position in reducing cavitation potential. Based on the integrated results of pressure, aeration, and cavitation index, the Series A configuration is recommended as the optimal position for spillways with a downward concave vertical curve geometry. This finding reinforces the established aeration theory reported in previous studies and provides a practical contribution to the optimization of aerator design in complex spillways.

This research intends to build a 3-D flow model of a section of the spillway chute at Tigadihaji Dam under the spillway design flood with a 1000-year return period, to investigate flow behaviour and the potential of cavitation damage using a numerical model in Ansys Fluent. The numerical model is validated against a physical model, and the impact of the aerator on the chute is also assesses. The research parameters are velocity, pressure, and cavitation number, obtained from the measurements at 16 points along the chute. The methodology consists of modelling and validation. The modelling was carried out for the chute and the chute with an aerator. The validation of computational fluid dynamics (CFD) model, based on pressure data, produced a determination coefficient (R2) of about 0.97. It shows that the CFD model is very good in presenting the trend and fluctuation of physical data. The cavitation analysis at Q1000 indicates a moderate risk in chuteway-3 and a high risk in chuteway-4. To mitigate this, a deflector–offset aerator was installed at the slope transition from 1:35 to 1:1.5. The simulation results reveal an increase of up to 0.1 in the cavitation index, with improvements extending about 20 m downstream of the aerator. Nevertheless, the offset section on the milder curved profile limited performance due to incomplete aeration.

This research intends to apply the multiplication sinus method to optimize two parallel reservoirs, namely the Tugu and Bagong reservoirs, in order to increase the efficiency of multipurpose water resource utilization for irrigation, raw water supply, micro-hydro electrical power (PLTMH), and flood control. The methodology consists of optimizing water allocation during low-flow conditions for the two parallel reservoirs with multiple purposes. For irrigation, the multiplication sinus method is used, while the other purposes are optimized using a simulation model with the objective function of maximizing the net benefit. Meanwhile, flood control under high-flow conditions is addressed through simulation by optimizing gate openings. The results show that the strategy of valve opening at the initial stage of a flood event significantly reduces the volume of flood storage required. This makes it possible to increase the reservoir water level, thereby directly increasing the potential of water energy without exceeding the river channel capacity downstream. Specifically, in the Tugu reservoir, flood storage is reduced from 1.8 million m³ to 1.3 million m³, with a peak discharge of 124.5 m³/s, which remains below the downstream river capacity (approximately 125 m³/s). Meanwhile, in the Bagong reservoir, flood storage can be reduced from 5.2 million m³ to 4.3 million m³, with a peak discharge of 41.9 m³/s, which is still safe and below the river capacity (approximately 44 m³/s). This efficiency proves that coordinated flood management between two parallel reservoirs can be carried out without sacrificing other interests. From the economic benefit perspective, the annual total value generated by the Tugu reservoir reaches a maximum of Rp. 136 milliard and a minimum of Rp. 117 milliards, with the main contribution coming from irrigation water supply. Likewise, the Bagong reservoir produces the highest annual benefit of Rp. 93.5 milliard and the lowest of Rp. 83.7 milliard, which comes entirely from irrigation.

This study examines flood risk conditions in the Juwana River watershed, Central Java, through the development of a quantitative framework that incorporates destructive power (H), vulnerability (V), and institutional capacity (C). Conceptually, the relationship among these components is represented by the fundamental risk formulation R = H x V/C. A GIS-based Multi-Criteria Risk Assessment (MCRA) approach was applied to integrate the hazard (H), capacity (C), and vulnerability (V) indicators within a spatial analytical environment. This conceptual model was subsequently calibrated through a non-linear regression procedure, resulting in the empirical formulation R = 0.695·H⁰·⁰³²·C⁰·²³³·V⁰·⁷¹¹. The analytical results demonstrate that flood risk is influenced by the combined effects of hydrodynamic characteristics and socio-institutional conditions. Areas undergoing rapid land-use transformation tend to exhibit higher levels of vulnerability due to increased exposure of populations and assets, whereas stronger institutional capacity is associated with reduced risk through enhanced mitigation, preparedness, and emergency response mechanisms. The analytical framework provides insights that may support informed decision-making in prioritizing interventions, allocating resources, and strengthening regional flood management practices.

This research assesses the variables influencing flood reduction. The land use changes occur due to the residential demand and all supporting infrastructures and facilities. It is related to population increase, raising surface run-off and then resulting in flooding. The proposed methodology involves simulating various placements of retarding basins (RAk) and different maximum storage capacities (Vk) for several flood return periods (QT). This research is conducted in the urban agglomeration area of Wonosari, Gunungkidul Regency, Daerah Istimewa Yogyakarta-Indonesia. The results show that the variable representing the maximum capacity of retarding basin (Vk) has a logarithmic relationship with the response of ΔQp, with a correlation value (R) of 0.7894 and an adjusted determination coefficient (adjusted R2) of 0.6207. In addition, the variable of the controlled watershed area ratio (RAK) has linear, quadratic, cubic, and quartic relations with ΔQp, with the average correlation value being 0.4563 and the average adjusted determination coefficient (average adjusted R2) being 0.2032. However, the variable of design flood for the T year-return-period (QT) has the logarithmic correlation, with a correlation value (R) of 0.3987 and an adjusted determination coefficient (adjusted R2) of 0.1536. Finally, the three variables of Vk, RAk, QT have a multiple linear relationship with ΔQp, with the correlation value (R) being 0.7894 and the adjusted determination coefficient (adjusted R2) being 0.6207. These results are essential to support the reduction of flood peak discharge modeling.

This research aims to develop a model for flood peak discharge reduction (ΔQ_p) through the placement of retarding basins within a watershed system, represented by the area ratio of the controlled watershed (R_Ak) and the maximum storage capacity of the retarding basin (V_k). The area ratio of the controlled watershed (R_Ak) is defined as the ratio between the catchment area of the retarding basin and the total watershed area (A_k/A). The methodology involves simulating various retarding basin placements (R_Ak) and different maximum storage capacities (V_k) for several flood return periods (Q_T). This study was conducted in the urban agglomeration area of Wonosari, Gunungkidul Regency, Special Region of Yogyakarta, Indonesia. The placement and utilization of retarding basins result in varying levels of flood peak discharge reduction (ΔQ_p) at the downstream control point (Taman Pancuran), depending on the maximum storage capacity of the retarding basin (V_k) and its placement within the watershed (R_Ak). The resulting empirical equations for flood peak discharge reduction (ΔQ_p) using the retarding basin method are as follows: ΔQ_p = 0.105654 − 0.014593 V_k − 0.029251 R_Ak + 0.011089 Q_T for V_k values in the range (V₁–V₄) = 36.4–208.8 × 10³ m³, and ΔQ_p = 1.374989 − 0.003702 V_k − 0.338381 R_Ak + 0.004773 Q_T for V_k values in the range (V₄–V₂₀₀) = 136.2–7039.1 × 10³ m³. An observed anomaly was identified, where ΔQ_p became positive at small values of V_k and R_Ak, indicating an increase in peak discharge (Qp).

This study aims to develop an integrated optimization model for water resources management in the Jatigede Reservoir by incorporating the influence of land cover dynamics on hydrological processes. The objectives are to improve the reliability of water allocation for irrigation, raw water supply, and hydropower while simultaneously enhancing ecological sustainability through land use planning. The methodology combines hydrological analysis using rainfall–runoff and dependable flow estimation, spatial assessment of land cover change based on the satellite imagery, and optimization modeling with multi-objective programming. Simulation scenarios were constructed to represent the existing conditions, spatial planning policies (RTRW), and optimized land cover management. The findings reveal that incorporating land cover factors into the optimization model increases water supply reliability by 5–10% and reduces the risk of sedimentation, thereby extending the effective lifetime of the reservoir. Moreover, the optimization scenario demonstrates that expansion of dry land forest cover contributes positively to water regulation, although it requires trade-offs with plantation forest areas. The novelty of this research lies in bridging the gap between technical water allocation models and spatial ecological considerations, offering a more comprehensive decision-support tool. This improvement provides valuable insights for policymakers in integrating reservoir operation strategies with land use planning to achieve sustainable water resources management.