Budi Indra Setiawan

A complete soil hydraulic model accounting for capillary and adsorptive water retention, capillary and film conductivity, and hysteresis

A soil hydraulic model that considers capillary hysteretic and adsorptive water retention as well as capillary and film conductivity covering the complete soil moisture range is presented. The model was obtained by incorporating the capillary hysteresis model of Parker and Lenhard into the hydraulic model of Peters-Durner-Iden (PDI) as formulated for the van Genuchten (VG) retention equation. The formulation includes the following processes: capillary hysteresis accounting for air entrapment, closed scanning curves, nonhysteretic sorption of water retention onto mineral surfaces, a hysteretic function for the capillary conductivity, a nonhysteretic function for the film conductivity, and a nearly nonhysteretic function of the conductivity as a function of water content (θ) for the entire range of water contents. The proposed model only requires two additional parameters to describe hysteresis. The model was found to accurately describe observed hysteretic water retention and conductivity data for a dune sand. Using a range of published data sets, relationships could be established between the capillary water retention and film conductivity parameters. Including vapor conductivity improved conductivity descriptions in the very dry range. The resulting model allows predictions of the hydraulic conductivity from saturation until complete dryness using water retention parameters.

Estimation of soil moisture in paddy field using Artificial Neural Networks

In paddy field, monitoring soil moisture is required for irrigation scheduling and water resource allocation, management and planning. The current study proposes an Artificial Neural Networks (ANN) model to estimate soil moisture in paddy field with limited meteorological data. Dynamic of ANN model was adopted to estimate soil moisture with the inputs of reference evapotranspiration (ETo) and precipitation. ETo was firstly estimated using the maximum, average and minimum values of air temperature as the inputs of model. The models were performed under different weather conditions between the two paddy cultivation periods. Training process of model was carried out using the observation data in the first period, while validation process was conducted based on the observation data in the second period. Dynamic of ANN model estimated soil moisture with R 2 values of 0.80 and 0.73 for training and validation processes, respectively, indicated that tight linear correlations between observed and estimated values of soil moisture were observed. Thus, the ANN model reliably estimates soil moisture with limited meteorological data.

Estimating Crop Coefficient in Intermittent Irrigation Paddy Fields Using Excel Solver

The current study proposes a novel method using Excel Solver to estimate, from limited data, crop coefficient (Kc) in paddy fields under intermittent irrigation (II). The proposed method was examined in a field experiment conducted at Karang Sari Village, Bekasi, West Java, Indonesia during the first rice season of 2007/2008 (December 2007 to April 2008) in the rainy season. As the control, continuous flooding irrigation (CF) was applied to the conventional rice cultivation fields. Based on the observed water storage, Excel Solver was used to estimate crop evapotranspiration. Estimated crop evapotranspiration was used to compute Kc value, then the average Kc values at each growth stage were compared with that for the CF treatment. The estimation method was evaluated by comparing estimated crop evapotranspiration and the crop evapotranspiration derived by the well established FAO procedure. Excel Solver estimated crop evapotranspiration accurately with R2 values higher than 0.81. Accordingly, more than 81% of the FAO crop evapotranspiration was described by the proposed method. Thus, Kc value could be well determined from those estimated crop evapotranspiration. Under the II treatment, the average Kc values were 0.70, 1.06, 1.24 and 1.22 for the initial, crop development, reproductive and late stages, respectively. These values were lower than those under the CF treatment for initial and crop development stages because of a minimal soil evaporation and intense dryness during these stages. However, average Kc values under the II treatment were higher than those under the CF treatment at the reproductive and late stages, indicating that the II treatment promoted more plant activity particularly for dry biomass production as indicated by a greater number of tillers per hill.

Climate change effects on paddy field thermal environment and evapotranspiration

The effect of air temperature increase from meteorological data on thermal microenvironment of irrigated paddy field is simulated using energy balance model. Statistical test was used to determine the existence of the trend in temperature change of data from meteorological stations in Indonesia. The temperature was tested to have positive trend, and it was used to generate future and past increase of temperature for the simulation. According to the simulation, the change in energy balance occurs following additional heat contributed by the increase of air temperature. The results show that irrigated paddy field seems to have function of decreasing effect of temperature increase whereas, evapotranspiration increases. However, increasing air temperature also increases temperature in paddy system, but seems to be more moderate than in nonpaddy field.

Performance of Quasi Real-Time Paddy Field Monitoring Systems in Indonesia

Since 2010 paddy field monitoring systems have been installed in ten locations in Indonesia. Each system performs quasi-real-time monitoring using a FieldRouter equipped with an in situ camera and connected to meteorological and soil data loggers. All parameters are measured and monitored at 30-min intervals. Data and field images are daily transmitted to a remote server through Internet connection. During experiments, field monitoring systems showed good performance in monitoring and transmitting field data. Quasi-real-time monitoring is more power-saving and Internet-cost-effective than real-time monitoring. However, its stability depends on the field solar power supply and Internet connection. If there are any problems with the Internet connection, power supply, or sensors, the field image and the data are lost. For minimizing problems in fields, it is best to involve local residents in maintaining the systems. We plan to develop an advanced data management system for analyzing the data with specific purposes bearing on climate change in the future works. Keywords: monitoring system, paddy fields, system of rice intensification, FieldRouter, quasi real-time.

A Field Monitoring Station Network for Supporting the Development of Integrated Water Resources Management

Field monitoring systems were installed in six locations of interest for field weather and environment monitoring in support of the development of an integrated water resources management system in two watersheds, Saba in Bali province and Jeneberang in South Sulawesi province, Indonesia. The stations were situated in lower, middle, and upper sections of the watersheds, with an intention of obtaining information regarding variation in weather and soil that represents variation in the parameters of the respective watersheds. The systems include an automatic weather station, a soil monitoring system, and a Field Router remote monitoring system that delivers data daily via Internet. Data handling procedures were developed to process the data and calculate the water balance of each field. The result yielded a description of the current condition of each field that can serve as a basis for local field water management assessment. This real-time monitoring network can support water management in watersheds that are facing water-related risks resulting from land-use change and climate change. Keywords: water resources, remote monitoring, climate change, agricultural water management.

Pixel Color Clustering of Multi-Temporally Acquired Digital Photographs of a Rice Canopy by Luminosity-Normalization and Pseudo-Red-Green-Blue Color Imaging

Red-green-blue (RGB) channels of RGB digital photographs were loaded with luminosity-adjusted R, G, and completely white grayscale images, respectively (RGwhtB method), or R, G, and R + G (RGB yellow) grayscale images, respectively (RGrgbyB method), to adjust the brightness of the entire area of multi-temporally acquired color digital photographs of a rice canopy. From the RGwhtB or RGrgbyB pseudocolor image, cyan, magenta, CMYK yellow, black, L*, a*, and b* grayscale images were prepared. Using these grayscale images and R, G, and RGB yellow grayscale images, the luminosity-adjusted pixels of the canopy photographs were statistically clustered. With the RGrgbyB and the RGwhtB methods, seven and five major color clusters were given, respectively. The RGrgbyB method showed clear differences among three rice growth stages, and the vegetative stage was further divided into two substages. The RGwhtB method could not clearly discriminate between the second vegetative and midseason stages. The relative advantages of the RGrgbyB method were attributed to the R, G, B, magenta, yellow, L*, and a* grayscale images that contained richer information to show the colorimetrical differences among objects than those of the RGwhtB method. The comparison of rice canopy colors at different time points was enabled by the pseudocolor imaging method.

Penentuan Awal dan Durasi Musim Kemarau Menggunakan Fungsi Polynomial dengan Aplikasi Visual Basic for Applications (VBA)

Forecasting the occurrence of the onset of dry season and its length is important in determining the availability of water for irrigation, domestic and industrial uses. The length of dry season is used for reference in calculating water demand. Prediction of drought can be studied based on the rainfall patterns that have occurred. This is possible because there is a tendency that the rain will repeat a certain pattern at a certain time. The purpose of this study was to predict the onset of dry and rainy seasons as well as their length. Determination of the onset of dry season and its length was conducted using polynomial function of the cumulative amount of rain every single day based on the rain data. The research was conducted using rainfall data from Climate Station III in Serang from 1989 to 2010. The sum of daily rainfall could form a polynomial function. If the magnitude of daily rainfall in a certain period of time is less than the slope of the cumulative annual rainfall, then at that time the dry season is occurred. Determination of the dry season peak can be done by finding the maximum (extreme) point from the polynomial function by getting the second derivative which value is close or equal to zero. In average, the dry season occurred in Serang city started on the 132nd until 300th day. Deviation value for the onset of dry and rainy seasons were 23 and 38 days, respectively, with an average of length of 168 days. The average of R2 value for polynomial function was 0.9937.

Increased fire hazard in human-modified wetlands in Southeast Asia

Vast areas of wetlands in Southeast Asia are undergoing a transformation process to human-modified ecosystems. Expansion of agricultural cropland and forest plantations changes the landscape of wetlands. Here we present observation-based modelling evidence of increased fire hazard due to canalization in tropical wetland ecosystems. Two wetland conditions were tested in South Sumatra, Indonesia, natural drainage and canal drainage, using a hydrological model and a drought-fire index (modified Keetch–Byram index). Our results show that canalization has amplified fire susceptibility by 4.5 times. Canal drainage triggers the fire season to start earlier than under natural wetland conditions, indicating that the canal water level regime is a key variable controlling fire hazard. Furthermore, the findings derived from the modelling experiment have practical relevance for public and private sectors, as well as for water managers and policy makers, who deal with canalization of tropical wetlands, and suggest that improved water management can reduce fire susceptibility.

Sustainable Water Management

Integrated water resources management (IWRM) is a key concept of water management in the twentieth century. The defi nition developed by the Global Water Partnership in 2000 is too penetrating the academic and decision-maker society. Although the concept of IWRM has a long history of more than 70 years, many critiques of the currently accepted defi nition have been generated by water scientists. Reconsideration of IWRM from the viewpoint of design science and especially sustainability science is important for creating new perspectives of IWRM. The use of IWRM toward a sustainable society was examined in relation to water sustainability and the evaluation of a water resources development project with sustainability. During the 7th World Water Forum (WWF7) in Korea in 2014, the Organization for Economic Co-operation and Development (OECD) proposed “Principles on Water Governance: From Vision to Action,” and the World Water Council (WWC) reported a discussion paper entitled “Integrated Water Resource Management: A New Way Forward.” Through the review of these international trends, the largest impact factor affecting IWRM is climate change. The infl uence of climate change on water issues became clear by the International Panel on Climate Change Fourth Assessment Report (IPCC AR4), and a strategic adaptation plan and methods for IWRM were proposed.