Abstract
A project was undertaken to create an inventory and generate relevant baseline information on household ponds in the Halda river watershed. This research is mostly belongs to Mapping and GIS analysis. At first all ponds are divided into two groups, large ponds (above 1000 m2 area) and small ponds (below 1000 m2 area). Then some important geometric and geographic parameters of large ponds are calculated. They are area, elevation and elevation wise distribution, neighbourhood distances, length, width, aspect ratio. Descriptive statistics are generated on these parameters and their mean, median, mode, sum, standard deviation, count, minimum, maximum etc. were calculated. Some informative charts are included in the result showing the findings. To calculate the area and total number of small ponds, intentional sampling is used. The average area of large ponds is about 2670 m2. The average elevation of these ponds is found 11.75 m. The mean neighbouring distance among these ponds is about 237 m and these ponds are rectangular shape in average because their average aspect ratio is 1.46 where aspect ratio 1.00 means the perfect square shape. The total area occupied by all ponds (both large and small) is estimated as 44.2 km2 and it is 2.63% of whole watershed area and 7.38 % of the valley area (here <20 m elevation and relatively plain). The total number of pond is estimated 43745 (large pond 6730 and small pond 37015) and almost all of them are in the valley area of Halda river watershed.
Highlights
The watershed of the Halda River is compacted with large number of water bodies
2.2.1 Calculating different geometric parameters of ponds in the attribute table of shape file (SHP file) In the attribute table of shape file of digitized ponds, different geometric parameters of ponds like area, perimeter, length, width, aspect ratio etc. were calculated using different formulas. 2.2.2 Excluding small ponds As we have only dealt with the large ponds in the first stage
At first the shape file of Halda river, It’s basin polygon file, it’s stream line file and other shape file such as shape file of ponds and Relative neighbourhood graph etc. was loaded in the GIS software
Summary
The watershed of the Halda River is compacted with large number of water bodies. From the trend it can be assumed that, in future, probably the culture of fish will mainly depend on artificial water bodies like ponds. The total area of the Halda River watershed is approximately 1683 km. The total area of the Halda River watershed is approximately 1683 km2 It falls in three districts of Bangladesh named Chittagong, Rangamati & Khagrachhari (Chowdhury, 2015). Mapping and GIS Analysis of Household Ponds in The Halda River Watershed. By precise onscreen digitization of these ponds, their geometric and other spatial parameters can be analyzed in GIS software Obtaining this information without remotely sensed image and GIS analysis would be expensive and somewhere impossible
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