Land Surface Evaluation Using Unit Hydrograph Methods at Way Besai Watershed, Sumberjaya, West Lampung, Indonesia

Sumber Jaya is an important water resource area for Lampung Province; therefore the local government protects this area, especially from clearing the forest for coffee plantation. However, the efforts in protecting the forest area had created conflict with the local farmers. The objective of this research was to evaluate catchments hydrological function from different land cover condition. The method using for this purpose was by investigating the unit hydrograph of each land cover which were observed from several rain events. The results showed that soil cover on each sub-catchment were relatively able to hold the input water. When rain falls, water was infiltrated into the soil before flow to the streams and water level increased slowly. When rain stops, water still flowed from the soil surface that water level did not decrease quickly. It can be concluded that the watershed surface was still in a good condition; however, watershed managements to prevent it from future destruction was necessary. The rest of forest area (12%) should be protected and no further coffee plantation in this area was allowed

Analisis Deret Waktu Curah Hujan Untuk Mengkaji Perubahan Iklim Di Daerah Tangkapan Air Propinsi Lampung TIME Series Analysis of Rainfall to Study Climate Change in Watershed Area, Lampung Province

One important climate factor for tropical area is rainfall. Changes in rainfall pattern will cause numerous problems especially in agricultural activities. Rainfall pattern could also lead to either flood or drought; problems which will not only affect agricultural activities but also socio-economic situation of broad community. Therefore, study of local climate variability focusing on rainfall related to the global warming is important. Time series analysis ( correlogram and periodogram) of daily rainfall was chosen to investigate the phenomena of global warming in local scale. Data (1974-2004) was collected from Sumberjaya, Air Hitam and Fajar Bulan; three stations located inside one of the important watershed in Lampung Province. From the collelogram, in general daily rainfall in this upland and forest area shows independency up to the year of 1990. No seasonal pattern could be an indicator that rains in this area are controlled more by local topography and land cover condition then by larger scale of climate system such as monsoon. After 1990 there were some weak sign of seasonal pattern. This could be interpreted as a sign that larger climate system started influence the local rainfall and as the global warming increases, it could be predicted that local rainfall pattern will be controlled more by the larger climate system. The periodogram shows that rainfall in this area has weak annual periodic. Data from Sumberjaya on 1990-1994 and 1999-2006 showed that annual periodic were getting stronger; a sign that larger climate system started dominating the area

Comparison of Different Models in Estimating Standard Evapotranspiration in Lampung Province, Indonesia

Evapotranspiration (ET) is the loss of water to the atmosphere by combined processes of evaporation from soil and plant surfaces and transpiration from plants. Since various factors affect ET, including weather, crops and soil parameters; numerous equations have been developed to quantify standard ET. The equations vary in data requirements from very simple, empirically based or simplified equations to complex, more physically based equations. This study used six methods in estimating standard evapotranspiration using data from September 2011‒August 2012 from Climate Station at Masgar (05o10\u2720” S, 105o10\u27 49”E, 50 m dpl) Lampung, Indonesia. The six models are: Hargreaves-Samani 1985 (H/S), FAO 24 Radiation (24RD), FAO 24 Blaney-Criddle (24BC), FAO 24 Pan Evaporation (24PAN), Linacre (Lina), and Makkink (Makk). The results were analyzed using statistics methods in error indicators, which are: Root Mean Square Error(RMSE), Mean Absolute Error (MAE), and Logaritmic Root Mean Square Error(LOG RMSE), while the closeness among the models was analyzed using Index Agreement (IA). Direct measurement had been done using lysimeters (3x2x1) m. The study concluded that Makkink model is the suitable simple model that should be chosen in Lampung lowland area to calculate ETo when climate data is limited, besides the recommended FAO 56 Penman Monteith

Evaluasi Metode Penman-Monteith dalam Menduga Laju Evapotranspirasi Standar (ET0) di Dataran Rendah Propinsi Lampung, Indonesia

Evapotranspiration is an important factor in estimating crops water use and then irigation schedule. Direct measurement of evapotranspiration is difficult since it is influenced by many factors. Estimation methods are developed for estimating evapotranspiration rate from meteorological data. One method which is recommended by FAO is Penman-Monteith Method (P-M). To evaluate whether this method could be accurately used in Lampung a comparison had been conducted with evaporation measurement on two climate stations in Lampung, Branti and Masgar with data set from 2006-2008. The result for Branti showed that observation data was lower than P-M for ET > 4 mm and higher for ET <4; while for Masgar evaporation observation always higher than P-M. In general P-M was 1.09 times higher than observation in Branti and 0.89 lower in Masgar. Correlation coefficients between P-M and observation were low (r = 0.3 for Branti and r= 0.5 for Masgar). Two possible reasons for the disagrrement were first, there was an error in measuring water level on the evaporation pan, this showed by the fact that observed evaporation has low coefficient correlation with all meteorological data which have direct impact on evaporation (air temperature and humidity, wind speed and radiation); second, CROPWAT converted shunshine duration to be the radiation intensity with linear approach while field data showed that sunshine duration did not relate linearly with radiation intensity

Effect of Rainfall Intensity on Glyphosate Herbicide Effectiveness in Controlling Ageratum Conyzoides, Rottboellia Exaltata, and Cyperus Rotundus Weeds

Glyphosate is one of herbicide active ingredient which is mostly used to control weeds in crops. However, in rain season herbicide effectiveness decreases as it is washed by rain. This research aimed to study effect of rainfall intensity  on the effectiveness of herbicide (Round up 486 SL 2.5 l/ha.) with isopropilamina glyphosate as the active ingredient in controlling specific weeds Ageratum conyzoides, Rottboellia exaltata, and Cyperus rotundus. The experiment was consisted of six treatments and arranged in randomized block design with 8 replications. The treatments were level of rain intensity which were 5 mm/hour, 10 mm/hour, 20 mm/hour, 40 mm/hour, no rain and control (no herbicide no rain). Rainfall intensity was determined by conducting simulation trials prior to the treatments and applied 30 minutes after herbicide applications. The results showed that herbicide effectiveness decreased as the rainfall intensity incresed, even though with longer time the herbicide was still able to control the weeds. The effect of rainfall intensity on herbicide effectiveness was different for different weeds. Up to intensity 40 mm/hour herbicide was capable to control weeds but with level of weeds destruction 20-60%