Articles

Respons Hidrologi Akibat Deforestasi di DAS Barito Hulu, Kalimantan Tengah

JURNAL MANAJEMEN HUTAN TROPIKA Vol 17, No 3 (2011)
Publisher : Bogor Agricultural University

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Abstract

The landcover change, particularly deforestation, can to affect of hydrological response on watershed.Deforestation of natural forest is identical to degradation of watershed functions, such as loos of land productivitydue to increased soil erosion, runoff, evapotranspiration, and decreased of water storage. The main objective ofthis study is describes the hydrologic response on the Barito Hulu watershed due to landcover change (particularlydeforestation) by the use Soil and Water Assessment Tool (SWAT) model. The result of the study showed thatdecreasing of forest area was 9.51% from initial condition can increase water yield, evapotranspiration, and erosion as much as 8.52%, 5.94%, and 1.73 t ha-1 year-1, respectively. Otherwise, water storage decreased as much as14.46%. The landcover on 1990 with rainfall 3,117.10 mm year-1 provided water yield of approximately 1,387.13 mm, evapotranspiration of 1,152.10 mm, water storage of 577.87 mm, and erosion of about 20.52 t ha-1 year-1. The landcover on 2003 with rainfall 2,613.2 mm year-1 provided water yield of approximately1,385.50 mm, evapotranspiration of 1,121.10 mm, water storage of 106.60 mm, and erosion of about 33.15 t ha-1 year-1 with erosion tolerance of about 43.57 t ha-1 year-1.Keywords: Barito Hulu watershed, land cover change, water yield, erosion, evapotranspiration

Dampak Perambahan Hutan Taman Nasional Lore Lindu Terhadap Fungsi Hidrologi Dan Beban Erosi (Studi Kasus Daerah Aliran Sungai Nopu Hulu, Sulawesi Tengah)

Jurnal Ilmu Pertanian Indonesia Vol 12, No 2 (2007): Jurnal Ilmu Pertanian Indonesia
Publisher : Institut Pertanian Bogor

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Abstract

The research was proposed to identify rainforest conversion impact on hydrologic function and soil erosion, and its simulation using ANSWERS model. Surface runoff and soil erosion were measured in soil erosion plots and outlet of Nopu Upper Catchment. Rainforest conversion to agricultural lands were significantly increased soil erosions and surface runoffs. Soil erosion from maize and peanut rotation was higher 2061.8% than natural forest. It higher value also in intercroping young age cocoa, maize and cassava and maize were 2023.8% and 2012.3% respectively. While surface runoffs increased up to 761.7°/o on bare plot, 567.5% on medium age cocoa, 446.8°/o on young age cocoa, 415.1°/o on intercroping young age cacao, maize and cassavas, 405.9°/o on old cocoa, and 329.5% on intercroping young age cacao and cassavas. Crop and management factor (C factor) value is significantly corelated with outputs of ANSWERS model. Using daily daily C factors, the ANSWERS model performs well in predicting soil erosion which is showed by determination coefficent (Jr = 0.89), model efficiency (0.86), and average of percentage model deviations (24.1%). Whereas using USlE C factor, model accuracy lower which represented by model coefficient (0.40) and average of percentage model deviations (63.6%). Using daily C factors, ANSWERS model simulation indicates rainforest conversion into agricultural lands on Nopu Upper Catchment has caused soil and water loss 3190.5 ton/year and 115441.0 m3/year, respectively. Agroforestry system practices in agricultural lands which in line with reforestation in stream line and steep agricultural areas (slope> 40°/o) was effective to reduce soil erosions up to 77.6°/o.

Intersepsi Curah Hujan di Hutan Hujan Tropis: Studi Kasus di Taman Nasional Lore Lindu Sulawesi Tengah

Jurnal Ilmu Pertanian Indonesia Vol 13, No 1 (2008): Jurnal Ilmu Pertanian Indonesia
Publisher : Institut Pertanian Bogor

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Abstract

This filed research was conducted from Apr 2006 to .Juni 2007 at natural tropical rainforest of the Lore Lindu National Park, Central Sulawesi. The objectives were to study the effect of rainfall properties and vegetation characters on interception losses through mathematical model approach, to estimate the rainfall interception losses and to determine the dominant factors influencing them. Observation of vegetation characters in the study area indicated that the vertical and horizontal structure were in good conditions with high leaf area index (LAI 4.8-6.43 m2.m-2 ), ground cover (68.5-92.59%) and wide canopy at average 5.59 (12.05-9.83 m2 Total rainfall (P) on the first measuring phase (Apr 2006-March 2007) was 1502,6mm for 172 events. Dominant rainfall depth was 0.5-5mm for 78 events with cumulative rainfall at 182.2mm or 12.3%, of P. Dominant rainfall intensity was 1--10 mm per hour for 121 events with cumulative rainfall 140.2 mm or 9.3 % of P. The mathematical relationship between rainfall properties and vegetation characters with throughfall, stemflow and interception loss show that rainfall depth and LAI are two factors that strongly influences as expressed: interception loss: Ic= 0. 786+0.343* P+0.051 *LA I (R2=73,77) Application of this equation and Gash model to the second measurement phase (Apr 2007-Juni 2007) gave good agreement on interception estimate and sensitivity, and considering data requirement and calculation procedure this equation is applicable for interception estimation. The critical point of this result is the rainfall properties on Lore Lindu National Park that is very important to forest management, especially in controlling of flooding. Keywords : rainfall interception, tropical rain forest, vegetation characters

MODEL PREDIKSI TIGGI MUKA AIR SUNGAI KALI GARANG SEMARANG DENGAN JARINGAN SYARAF TIRUAN

TEKNIK Volume 29, Nomor 3, Tahun 2008
Publisher : Fakultas Teknik, Universitas Diponegoro

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Abstract

One of the big rivers flowing in center of Semarang city is Garang river with watershed area about 220km2 and having characteristic such as big flood discharge and flash flood. Where flash flood on January25th 1990, caused more than 45 people died and goods losses until 8.5 billion rupiahs. One of some modelsto pedict water level is used black box model. Artificial Neural Network one’s of the black bock model . Inthis research, Artificial Neural Network (ANN) with back propagation method is used to predict waterlevel in Garang river where as input are rainfall in upstream of Garang river during two days, while asoutput is water level in downstream of Garang river for two hour later. Result of optimum predicting haveMSE 0.0037 and average of error 1.18 %.

Modeling of Water Table Fluctuation on Tidal Lowland Area of B/C Type: A Case in South Sumatra

Forum Pasca Sarjana Vol 33, No 2 (2010): Forum Pascasarjana
Publisher : Forum Pasca Sarjana

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Abstract

The objective of this research is to develop a model of water table fluctuation on tidal lowland area of B/C type.  Modeling of water table is expected to support the agriculture development on tidal lowland area, especially on water management due to the important role of water management in the agriculture on tidal lowland area. The water table controls on the particular depth can support the farming system and avoid pyrite oxidation. The model of water table fluctuation which is developed in this research based on the ellipse concept. The developed model has been tested on the tidal lowland areas in P6-3N Delta Telang I, Banyuasin District, South Sumatra Province. The simulated model showed the promoting result in estimating the depth of water table on tidal lowland area of B/C type. The developed model could explain the proportion of water table depth variation between 89.5% up to 94.7% with standard error estimation varied from 0.029 to 0.042 meters. The model has high sensitivity to the parameter of the water level in the tertiary canals.   Key words: modeling, water table, water management, tidal lowland area of B/C type

The Effectiveness of Micro Fertigation System for Small Plots

Forum Pasca Sarjana Vol 32, No 1 (2009): Forum Pascasarjana
Publisher : Forum Pasca Sarjana

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Abstract

The aim of the research is to evaluate the effectiveness of micro fertigation system and application of cows fermented urine (uriferm) for chili (Capsicum annum sp.) Cultivation.  The micro fertigation system with 0.5 mm inside diameter micro-tubing is used to control the flow from outlets along lateral.  The lateral with 5/16 inch inside diameter is made of soft PVC hose.  The result of the research showed that the micro fertigation system is running well. Randomized block design with four replications are used for the field experiment.  There are four treatments i.e. conventional culture by watering can (A), uriferm fertigation (B), non uriferm fertigation (C), and Hartus formula fertigation (D).  The laboratory analysis showed that the properties of uriferm increase in composition compared to non uriferm and used successfully as nutrition.  The micro fertigation system showed better result compared to the watering can on variable observation of plant and root development of chili.  The field experiments showed that the micro fertigation system significantly reduced volume of water used by 49.5% and raised chili yield by 61.2% compared to watering can.  The uriferm fertigation (B) showed better result compared to other treatments on wet weight of chili and water productivity.  The total income from 390 m2 irrigated land with micro fertigation system was about Rp 2,961,700,00/season and  feasible to apply with B/C ratio =  1.51, IRR value = 27.49% and NPV = Rp 387,413.83 at discount rate 9% per annum.   Key words: micro fertigation system, uriferm, chili, water productivity, small plots

Sustainable Groundwater Management Model for Pump Irrigation at the District of Wajo in South Sulawesi Province

Forum Pasca Sarjana Vol 31, No 3 (2008): Forum Pascasarjana
Publisher : Forum Pasca Sarjana

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Abstract

Groundwater in the District of Wajo is stored in Siwa-Pompanua basin covering an area of 93,900 ha and discharge of around 379 millions m3/yr.  The groundwater is utilized to irrigate rain-fed rice fields privately by farmers by means of wells.  The distance between wells and pumping rate are designed without considering the characteristics of the aquifer and adequate irrigation management so that damage in environment might occur and consequently farming might not be sustainable.  A research was conducted with the objectives to study the aquifer characteristics and to develop environmentally friendly groundwater management.  Mathematical models were developed by combining equations of conservation of fluid mass (continuity equations) and Darcy’s law, whereas models of groundwater management were based on crop water requirement and aquifer characteristics.  Test of the model resulted in coefficient of determination equal to 0.848 for the prediction of the drawdown groundwater head.  The result of the model optimization indicated the optimum discharge of each of the wells was different.  One of the wells had a the biggest discharge of 1,268.33 m3/day irrigating 27.58 ha and one other  of the wells had a the smallest discharge of 279.54 m3/day irrigating 6.08 ha of paddy fields based on the irrigation water requirement of 45.99 m3/ha.day.  The reasonable minimum area (ha) determined with equation of power function in x, where x are irrigated hours per season.  For one of planting season/yr, the coefficients of the power (α) equal to 0.0123 and the power functions (β) equal to 0.7247, while for two of planting season/yr with α equal to 0.0047 and β equal to 0.8413.   Key words: sustainable groundwater utilization, paddy field irrigation, groundwater management model

Prediction of runoff, sediment yield and their quality using ANSWERS model at Batujai reservoir area, West Nusa Tenggara

Forum Pasca Sarjana Vol 16, No 1 (1993): Forum Pascasarjana
Publisher : Forum Pasca Sarjana

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Abstract

The possibility of ANSWERS model application for predicting runoff and sediment yield is discussed in this paper. Three types of rainfall duration (e.i. 6; 8 and 10 hours) with three amount of total rainfall of 100; 200 and 300 mm and two different systems consistink of four kinds of land use were used for simulating runoff and sediment yield. The result showed that the runoff initiation was identified at 189 minutes from the start of rainfall when the amount of rainfall total was 200 mm with 8 hour duration (about 0.0001 inch/hour). The initial sediment yield was shown to be about 0.45 kg at 188 minutes from the begining of rainfall when rainfall total w+ 300 mm with 6 hour duration. Actual runoff and maximum sediment yield were recorded about 0.0017 inchlhour and 12.000 kg respectively. The land use which were considered as potential for erosion protection were mixed gardpn and wet rice. The considered land use would reduce runoff and sediment yield about 50% than traditional land use. The type of output indicates that ANSWERS model is promising for predicting runoff and sediment yield.

Rainfall Interception Effects of Energy and Mass Transfer in Tropical Raiforest: Case Study in Lore Lindu National Park, Central Sulawesi

Forum Pasca Sarjana Vol 31, No 4 (2008): Forum Pascasarjana
Publisher : Forum Pasca Sarjana

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Abstract

The field observation of this research was conducted from June 2005 to May 2007 in tropical rainforest at Lore Lindu National Park, Central Sulawesi.  The main objectives of this research were to study (i) the relationships between interception loss and rainfall properties and vegetation characters and to determine the dominant factors affected, (ii) the effect of rainfall interception on energy flux and mass transfer, and (iii) the dynamics of vertical energy flux under the forest and grass land. Rainfall interception was 36.34% of gross rainfall in 200 events, Depth rainfall and LAI factors had strong effects on rainfall interception.  The relationships could be expressed as Ic = 0.980+0.239P+0.035LAI (R2 = 0.78).  The output of this equation was compared with Gash model and the observation value showed that deviation of the equation was 1% and less than Gash model, so that equation gave as good result as Gash model gave.  By considering the data requirements and calculation procedures it was concluded that this equation is applicable for interception prediction.  Land use type had effects on radiative and energy balance.  Net radiation (Rn) in the forest was 10.66 MJ/m2/day and higher than in the grass land where incident global radiation was similar.  Vertical latent heat flux in the forest was 9.53 MJ/m2/day or 89.40% Rn in rainy day and 8.41 MJ/m2/day or 74.56% Rn in dry day, on the other hand, in the grass land, sensible heat flux was higher than latent heat flux of all weather condition.  Direct effect of rainfall interception on energy flux and mass transfer it is needed latent heat about 9.0 MJ/m2/rainy day to evaporate the rain intercepted 3.69 mm/rainy day.  Effect of rainfall interception had positive correlation with  latent heat flux and the negative correlation  with sensible heat flux.   Key words: interception, energy, mass and tropical rainforest

Analysis of Bekasi City Flood Reduction Using Watershed Management

Forum Pasca Sarjana Vol 34, No 1 (2011): Forum Pascasarjana
Publisher : Forum Pasca Sarjana

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Abstract

One major river flowing through Bekasi City is Bekasi river. Total extent of the Bekasi watershed is about 39.045 ha, in 2002 with rainfall of 250 mm for 8 hours caused about 138 ha flooded in residents area for 2-3 days in Bekasi City, more extremely in 2005 with rainfall only 127 mm  for 6 hours caused about 164 ha flooded in residents area for 3 days.  This evidence showed that flood problem in Bekasi City is become worse, and seem to be more horrifying in the future. Therefore, the flood problem needs an extremely great attention.  The objectives of the research is (1) analysis watershed condition; (2) analysis of the causes of flood over Bekasi City from the perpective of hydrology and hydraulic; (3) plan of Bekasi watershed management to reduce flood risk in Bekasi City.  To obtain the purposes of this research, the method of analysis is devided into four main subjects: (1) analysis of watershed condition using SCS method; (2) hydrology analysis using hydrology modeling HEC-HMS; (3) river flow capacity using hydraulic modeling HEC-RAS and (4) plan of scenarios to reduce flood risk.  There are four scenarios to overcome the flood problems: (1) similarly with government plan 2010;(2) managing Bekasi watershed area with conservation tillage; (3) build water retarded structure entire of  watershed and;(4) combination of second and third scenarios.  The research results shown that river flow capacity only 462 m3/s is not enough to flow the discharges, otherwise the land use is change and increasing the run off in upstream.  Based on the problems, it is expected to overcome the flood problem by managing Bekasi watershed area with conservation tillage and build water retarded structure.  It will reduce 28.58% of the discharge run off in 2020.   Key words: flood, land use changing, watershed management