Kriging Infill of Missing Data and Temporal Analysis of Rainfall in North Central Region of Bangladesh

Abstract

The north-central region of Bangladesh is subjected to rapid land use pattern changes as a result of continuous unplanned urbanization, encroachment of water bodies and agricultural land, filling up of designated wet lands and flood flow zones by real estate companies. There is a growing need to consider rainfall regimes an important factor in assessing drainage network design, flood control work, soil and water conservation planning, watershed management and likes. The historic data of daily rainfall of 7 climate stations in the area comprising 4 districts of Dhaka (Banani, Savar and Dhaka_PBO), Narayanganj (Shimrail), Narsingdi (Narsingdi) and Gazipur (Joydebpur and Maona), 4 of which are for 30 years (1984-2013), 1 is for 21 years (1993-2013) and 2 are for 18 years (1996-2013). An assessment of Kriging infill is conducted and appreciable results confirmed for a missing station from moderate values of nearby observed rainfall. The missing volume of data is identified as 7.95% and infilled by Geostatistical approach Kriging in Arc-GIS 10.1. The Kriging generated data and the observed set of data are both then analyzed station-wise for temporal variation on yearly, monthly and seasonal basis. Kriging yields most significant results for monsoon and pre-monsoon seasons. Localized trends are observed at all stations. Kriging Average Annual Rainfall (AAR) and total rainfall values are higher than observed ones; highest AAR of 2047 mm at Dhaka_PBO and lowest 1322 mm at Joydebpur; the highest monsoon rainfall of 1343 mm is at Maona, the highest pre-monsoon rainfall of 465 mm is at Dhaka_PBO and the highest post-monsoon rainfall of 208 mm is at Shimrail.