4. Observations and Data 4.1. General Kegalle District Which Is Under
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4. Observations and Data 4.1. General Kegalle district which is under Sabaragamuwa Province, of Sri Lanka, lies between the two major cities Colombo and Kandy. It has a land area of 1663 Sq.km with the population of about 731,590 as per the National Census of (1991). Population density of the area is about 440 persons/ sq.km which is nearly double the national average of 257 persons/ Sq.km. The selected area of Gurugoda Catchments (Figure 6) covers a part of 4 Divisional Secretary Divisions namely Warakapola, Galigamuwa, Kotiyakumbura and Ruwanwella. The Gurugoda watershed starts from Kandy district near Aranayake and covers 23,000 Ha and five Agrarian Services Centre areas and seventy-eight Gramaniladhari Divisions. Kegalle district in the Wet Zone experiences two rainy seasons namely Maha and Yala. The most likely mean annual rainfall receives in this area range from 1500mm to 5500mm (ID 1984). The study area which is the Gurugoda Catchment is situated in the Southern part of the district and receives more rain than the District average. Average annua) temperature of the area is 28° Celsius According to the agro ecological map four zones can be identified in the study area i.e. Wet zone Up Country (WU), Wet zone Low Country (WC), Wet zone Mid Country (WM), and Intermediate Low country (National Atlas 1981) (Figure 7 ). Gurugoda watershed mainly consists of hilly areas with elevation ranging from 30m to 1100m above mean sea level. The topographic map shows that most of the parts consist of steep slopes. Because of the steep slopes, very often during rainy seasons, flooding and also land slides occur in the down stream areas. The available soil maps indicate that the predominate soils in the study area is Red Yellow Padzolic soil (Ultisols) and Reddish brown Latozolic. The vallev bottoms are covered by alluvium and colluviums which are mainly used in these areas of paddy cultivation. 4-1 4-1a 13 AGRO-ECOLOGICAL REGIONS OF SRILANKA FIG. 2.3 REFERENCE Agro • Ecological Region Boundory Regional Research Centre Of Institute Research Station SCALE 24 MILES TO AN INCH IN Ot AN OCEAN R • P'ODUT »D FROM I arid ond Wofif Oiwiaton, 0<(IC1FMNI ol AGMCULTUI*, Figure: 7. Agro-Ecological Region in Sri Lanka Page 4-lb 4.2 Data collection. 4 Data for the study were of two types primary and secondary. Primary data were collected by site visits, from farmers and settlers in the area through interviews and discussions Field Officers who are carrying out duties in these regions were utilized as a source of data and hence information was also collected from them. The officers consulted in the agriculture sector were the Grama Niladharies, Agriculture Instructors, Divisional officers and Govisevana Niyamakas. 4.2.1 Field Data Collection The field data collection consisted of two objectives. One is the verification of existing land use and soil types with that obtained from the 1:50,000 topo and soil maps. The other was to identify soil erosion level actually observed in the field. Only a handful of field data collections could be found from published sources. The field data collection sheet of Morgan(1995), was taken as the initial document for data collection. This sheet was modified to capture the essential information for this study. Initially an attempt was made to collect data using the University of Moratuwa Premises ((10 Ha) as a sample site. In this exercise the trained data collectors were used for data collection . This study revealed the needs of a pre coded data collection method for easy and quick field data pickup. Also this initial surveys revealed the difficulty of data collection based on a grid based coverage that was cited in Literature. As such the preliminary studies used foot paths and roads to cluster spatial units for easy data pickup. Repeated data collection attempts at the University premises showed that a combination of a field sheet and a map would be better to collect the type of spatial data that are needed in this type of a study The modified preliminary data sheet was pilot tested in the Pallepalpita Sub watershed (12sqkm) of the Gurugoda watershed. In this it was identified that details of picking data requires adjustment due to the vastness of the spatial extent. Since the data collected are to be used in the scale of 1:50,000 and that the outputs would be used for planning purposes, spatial clusters for data collection needed adjustment. ^===^^ 4-2 Final Field survey was done based on spatial clusters using footpaths, cart tracts and motorable roads. The process of field data collection questionnaire development, and the methodology refinement is explained in tabular form (Table 15). Questionnaire was prepared to suit the purpose of data collection from various types of personnel. It was prepared in Sinhala and English language and appears in Annex 2 & 3.Information collected from the personnel was regarding the land use present and history, farming methods and practices, use of conservation practices, in case of soil loss from a particular area and details of previous landslides. Soil types in the watershed area were also assessed using a field data collected form with the help of Govi sevana Niyamaka personnel. Field identification though initially attempted to identify seven erosion classes, had to restrict them to three, due to the difficulty in picking up minor differences between classes. Field data collection was done using a pre coded land use, slope classification method. Land use types were restricted to the seven types which were identified from the 1:50,000 Topo Map. Map of 1:10,000 were used to initially pickup information (Annex 4) and information so obtained were them taken to 1:50,000 topographic maps (Annex 5). Critical and moderate areas of soil erosion were identified and mapped on 1:10,000 scale separate sheets for each visited village. Field data collection was done in twenty-seven villages and sixty-five spatial locations that were either significantly or moderately eroded, were mapped (Figure 8). In the other areas in villages that were visited had either no or negligible erosion hazard. Land use extents collected during field surveys were verified with the 1:50,000 topographic maps Field data collection was mostly concentrated on two spatial areas. One is in the NW of the watershed at Galigamuwa Divisional Secretary area and the other is in the NE area of watershed at the same Division. 4.3. Secondary Data. Secondary Data collected for the study consist of rainfall, soil type and Topographic maps, and land use information. Soil Erodability and Erosivity factors taken from studies done in Sri Lanka. 4 Field Identified Erosion Levels - Gurugoda Watershed N Kotapola Minor Road Main Road-B Jeep/Cart Track Severe Erosion Moderate Erosion Negligible Erosion 8 Kilometers Figure 8 : Field Identified Erosion Levels 4-3a 4.3.1 Rainfall Since the Soil erosion potential could be related to the annual rainfall, annual rainfall in the study area was collected from the Department of Meteorology. Three Meteorology Department rain gauges were in the vicinity. The map of rain gauge stations and the data availability were given in table 4.1 and shown in Figure 9 Table 4.1 Average Annual Rainfall in the Study Area Data Average Rainfall Station Availability Annual (years) Rainfall (mm) 1 Dunedin(Dehiowita) 1983- 1999 3724 2 Ambanpitiya. 1983 - 1999 2423 3 Yataderiya(Undugoda) 1983 - 1993 3381 4.3.2 Soil Types Soil map of the study area shows three major soil types in the area of concern. They are Red yellow Podzolic (Ultisols), Reddish Brown Latazolic and Immature Brown Loams. The soil types in that area was verified using field visit information and obtaining the assistance of Agriculture Instructors who are working in Galigamuwa Divisional Secretary Area. Most parts in the District consist of Red Yellow Padzolic soils and it covers nearly 65% of the agricultural lands. The soil type distribution of the study area was given in Table 14 and shown in Figure 10. 4-4 4 j Ambanpitiya Dunedin Yataderiya v.. - ailiiiiilglp1 S Kilometers Figure 9 : Thiessen Polygons for Rain Gauging Stations - Gurugoda Watershed 44a3 a Red Yellow Podzolic Reddish Brown Latazolj i I Immature Brown Loam N s ure 10. : Soil Distribution in Gurugoda Watershed 4-4 b Table 4.2 Soil Types and Extent in the Gurugoda Watershed Soil Type Extent (sq\km) Distribution % 1 Red Yellow Podzolic 172.10 74.6 2 Reddish Brown latazolic 56.55 24.5 Immature Brown Loam 2.01 0.9 Total 230.6 100 Table 4.3. Issues Identified and Modification to Field Data Collection Sheet Stages of Field Data Issues Modification Sheet Development Climatic condition as rainfall, Such unimportant fields Initial Erosivity and mean temperature not were removed from the possible to collect from field level.. form. Data collection form was found not Gullies, soil type ,land Pilot testing necessary . 1:1,000 scale map was use and slope class can (University used to capture and note the data. be mapped on same Premises) The Gird based data capture was map. Data capturing possible was based on grid base. I km x 1km grid was selected and Grid basis data Pilot testing in attempts to collect information on collection is not Kegalle(Pallepal enlarged l:10,000scale map. poved possible. Footpath and pita watershed) difficult. cart track used to identify spatial clusters. Gurugoda Administration boundaries were used Separate map was used watershed as spatial units. Also cart tracts, foot for each village and (study area) path and some motorable roads were marked field used to demarcate the boundaries.