Due to channel sedimentation, water deficits and flood still becomes problems in Katingan tidal irrigation system, while the stakeholder plans to reclaim new area in the presence of pyrite soil. This research aims to overcome these problems through four water management scenarios simulated using HEC-RAS to meet the needs of water supply, flushing and drainage. The result shows that water leaching requirement for existing area is 2.48 million m3 and could only be fulfilled by canal normalization. Moreover, extended network with narrow intake canal supplies less than 4.3 million m3 water leaching, so that wide canal connected to the river is required to facilitate more water flowing into the system. Related to flushing, installing pumps in the middle intake could increase canal circulation with one-way outflow during ebb tide, while the inflow depends on flap gates at the same position. Furthermore, the volume of rainwater is generally able to be discharged for every rainy day by all scenario designs. However, existing condition and network expansion with narrow intake canal have less rainwater deficit duration. In conclusion, leaching and drainage aspects require more water storage and wide canal intake, where flushing criterion need the use of pumps and gates.

The Peatland Restoration Agency of the Republic of Indonesia (BRG-RI), an agency that is mandated to restore 2 million hectares of degraded peatland by 2020, has developed a 3-R approach towards tackling the problem based on the program of rewetting, revegetation, and revitalization of livelihood for the peatlands restoration in Indonesia. The Rewetting program that aims to rehabilitate hydrologically a peatland to a near natural state is carried out by canal blocking, canal backfilling, and construction of deep wells. To know the progress of the restoration activities by BRG, it is very important to understand the effectiveness of canal blocking on rewetting of the tropical peatland. The effectiveness of canal blocking was investigated through the monitoring of groundwater level (GWL) fluctuation around the canal block. This study was carried out at a canal block that is located at the peatland of Sungai Tohor Village, Kepulauan Meranti Regency, Riau Province. For monitoring of GWL fluctuation as the impact of canal blocking, five dipwells were set at the peatland that are perpendicular to the canal with the distance of 20 m, 70 m, 120 m, 170 m, and 220 m respectively. The results of this study show that the impact of canal blocking could raise the water table in the peatland at the radius of about 170 m from the canal. The radius impact of the re-wetting might be bigger or smaller, that strongly depends on the hydrotopography situation of the area.

Flood forecasting at Wonogiri Reservoir is restricted on the availability of hydrologic data due to limited monitoring gauges. This issue triggers study of unit hydrograph modeling using Geomorphological Instantaneous Unit Hydrograph (GIUH) which is based on Geographic Information System (GIS). Analysis of physical watershed parameters was conducted on Digital Elevation Model (DEM) data using software Watershed Modeling System (WMS) 10.1 and ArcGIS. Nash model and S-curve method were used to process triangular GIUH into hourly Instantaneous Unit Hydrograph (IUH) and Unit Hydrograph (UH) and then was compared with the observed UH of Collins method. A sensitivity analysis was conducted on parameter of RL and Nash-model k. Evaluation of accuracy of the simulated GIUH runoff hydrograph was also conducted. The GIUH model generated UH with smaller peak discharge Qp, also slower and longer of tp and tb values than the observed UH. Accuracy test of the simulated GIUH runoff hydrograph using Nash-Sutcliffe Efficiency (NSE) shows that Keduang watershed gives a satisfying result, while Wiroko watershed gives less satisfactory result. The inaccuracies occur due to limited flood events used to derive the observed UH and stream tributaries that were not properly modeled based on Strahler method.

Peatland wildfires, especially in tropical ecosystems, are often caused by drought, and lead to smoke and other related problems in all aspects of community life in Indonesia, especially in Central Kalimantan. Drought is worsened by the number of dry days in the dry season, known as the El Niño phenomenon, and the drainage system in a peatland. Additionally, drought decreases the water table and increases the probability of occurrence of wildfires in peatland areas. This study aims to modify the numerical formula of the drought factor (DFt) in the Keetch–Byram drought index (KBDI) based on tropical peatland wildfire conditions in Central Kalimantan during the El Niño phenomenon in 2015. Furthermore, it applies a revised peatland water table reference of 400 mm below the ground surface, based on previous research and the Government regulation on peatland ecosystem protection and management in Indonesia. These El Niño conditions caused a rain decline of approximately 35% in Block A, Ex-Mega Rice Project, Mantangai sub-District, Kapuas District, Central Kalimantan Province. The modified KBDI is compared with the Number of Fire Alerts (NFA) using NASA’s Active Fire Data in 2015. The analysis results demonstrate that the modified DFt under tropical peatland conditions leads to an increase in the drought index value, beginning on the driest days between July and November 2015. The value of the KBDI drought index increases from the high to the extreme index from September to November 2015, when as many as 61 extreme drought indices became indicators for peatland wildfire risk assessment. The extreme KBDI is directly proportional to the NFA recorded during 2015, and the highest number of fire alerts is observed for October 2015, with 1746 fire alerts within 31 days and extreme drought indices from 27 days. Hence, this modified formula is suitable for wildfire conditions on this peatland in Central Kalimantan. Overall, the modified DFt can be successfully applied to the El Niño phenomenon in 2015.

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