Chay Asdak

Factors affecting runoff and soil erosion: plot-level soil loss monitoring for assessing sustainability of forest management

Abstract The assessment on key ecological factors affecting runoff and soil erosion and the usefulness of plot-level monitoring of soil erosion was conducted by collecting runoff and soil loss records from 14 runoff plots. The runoff plots were set up in two catchments in Central Kalimantan, Indonesia, where conventional logging and Reduced Impact Logging (RIL) took place. Runoff plots were set up in forest areas with different levels of logging disturbances, i.e. harvesting areas (four plots), skid trails (six plots), and undisturbed/control areas (four plots). The magnitude of runoff and soil loss from skid trail plots were found to be the highest, followed by control plots and harvest plots. Canopy cover, sapling density, litter depth and woody debris appeared to be important ecological factors that determine the magnitude of soil loss. Tree canopy determines the size and erosive power of the raindrops. Sapling, litter layer, and woody debris protected soil surface, thus preventing soil detachment, and provided surface roughness that minimised soil particle movement down the slope. The roles of these ecological factors were less significant compared to rainfall in determining the magnitude of runoff. Canopy cover, sapling density, litter depth and woody debris can be measured quantitatively or qualitatively without complicated equipment and methods. Furthermore, they are sensitive to logging disturbance which make them suitable verifiers of soil erosion. Forest managers need to limit disturbance to these factors in order to minimise soil erosion in their logging operation areas. Monitoring of soil loss using runoff plots was cost-effective and provided valuable information about soil erosion risks caused by logging operations. Runoff plots clearly demonstrated site disturbances where the plots are located. Monitoring allowed more direct linkages to be made between management practices and their impacts on runoff and soil erosion, thereby enabling forest managers to identify problems and take appropriate preventive measures to improve their management practices.

Rainfall interception loss in unlogged and logged forest areas of Central Kalimantan, Indonesia

Abstract Rainfall interception losses were monitored for 12 months, and related to vegetation and rainfall characteristics at the BPK-ECTF research site (Wanariset Sangai) on the upper reaches of the Mentaya river, Central Kalimantan. The rainfall interception losses were quantified, based on the records of 55 selected rainfall events within the range of 8.5–135.5 mm in the unlogged forest, and 95 rainfall events in the logged-over area. Over a 6-month-period in 1 hectare of pristine, unlogged, natural, tropical rainforest, the total amount of rainfall interception loss was 251 mm or about 11% of total gross rainfall. In the logged forest, the total rainfall interception loss over 12 months was 219 mm, or 6% of gross rainfall.

Evaporation of intercepted precipitation based on an energy balance in unlogged and logged forest areas of central Kalimantan, Indonesia

The effect of logging practices on rainfall interception loss has been investigated in a humid tropical rainforest of central Kalimantan. The traditional volume balance method was used to measure throughfall, stemflow and interception loss. The evaporation rate during and after rainfall has ceased in canopy-saturated conditions was calculated by an energy balance method, which relied on the modified Penman equation using directly determined microclimatic and canopy structure variables as inputs. The results obtained showed that the evaporation from wet canopies in this research area is driven more by advected energy than by radiative energy. In the unlogged plot, advective energy accounted for 0.38 mm h ˇ1 of the 0.51 mm h ˇ1 of evaporation, whereas radiative energy accounted for only 0.13 mm h ˇ1 . A similar relationship between the major driving variables and the rate of evaporation was also found in the logged plot and this implies that logging activities did not change the proportion of energy used for interception loss. The Priestley‐Taylor equation was found to be a poor model for evaporation of intercepted water in tropical forests because advected energy is very important at the canopy scale. # 1998 Elsevier Science B.V. All rights reserved.

Towards a water balanced utilization through circular economy

Purpose The purpose of this study is to describe and explain the relative water scarcity condition as one of the main problems encountered in Indonesia. It is caused by fierce competition between water users, water over consumption and high water price. The water conflict and increasing phenomena of relative water scarcity result in unequal access to water between the rich and the poor. This research is intended to contribute to a balanced water governance system that secures equal and fair access to water resources for all users. Design/methodology/approach A mixed method approach was used involving interviews with the owners of the established bottled water companies, the community leaders, guard for sluice gate, local NGOs and several government agencies. Findings Research results indicate that water policies and implementation are lacking coherency. It is also shown that the complex government structure with responsibilities divided over multiple agencies is responsible for this. The circular economy for water governance system used to find alternative solutions for reducing social conflicts so that the water will be made available to those who have no water access. Research limitations/implications This research used only one location with a representative number of interviewees; hence, the findings are not possibly generalizable. Originality/value The combination of water legal framework and circular economy concept was used to reduce water scarcity