CS (AR) / 2009-10: A study on spatial and temporal hydrological aspects of Kakinada city

Abstract

It is well known that changes in land use have direct effect on the hydrology any watershed. Among such changes, the urbanization is the most forceful one that affects the water balance of any system under study. Urbanization can have a great effect on hydrologic processes, such as surface-runoff patterns. Neglect of the hydrology of the region while undertaking planning and developmental works in an area will have serious consequences. Apart from the non-availability of drinking water, the other problems of concern of urban areas and rural housing projects, due to this negligence, are the inundation of dwelling areas during rainy season due to improper roadside drains and storm water drains; flooding of low-lying areas etc., A detailed study on hydrological aspects of Kakinada city was undertaken with the objective to understand short duration rainfall characteristics as input for use in water resources planning and management. The highest amount of rainfall recorded in one, two and three hours at Kakinada are about 70 mm, 120 mm and 135 mm respectively from the hourly IMD Data. The intensity of rainfall is about 200 mm/hour for about 15 minutes during October 2005. The maximum 1, 5, 10, 15, 30 and 60 minute rainfall intensity recorded up to 2009 was during 30th August 2009. During the intense storm of 30th Aug 2009 an intense rainfall of 20 cm/hr over 5 minutes; 16.5 cm/hr over 15 minutes; 11.5 cm/hr over 30 minutes durations occurred in the city. Also, it is noticed that rainfall intensities were higher for storms of lower durations during the study period. It is to be mentioned that 2009 is a deficit rainfall year of recent decades. From the DAD plots, the area of core of storm centre was 37.7 Ha for 30 minutes duration with rainfall of about 26 mm in the middle parts of the city during the August 2008 storm event. Analysis of less or small rainy events indicated that rainfall intensity of 1 (0.25 mm) to 2 tips (0.5 mm) in 15 minutes might initiate runoff from RCC surfaces. From the groundwater investigations aspect, it is observed that the deficient rainfall of 2008 has resulted in large EC of groundwater during post-monsoon of 2008 in the eastern half of the city and is very high compared to the EC of Post monsoon of 2007. It is observed that at Madhava Nagar, which is adjoining good recharge area like JNTU campus and Medical college sports grounds extending up to district sports authority campus experience a rise of 1.2 m for every 300 mm of uniform rainfall under wet conditions indicating a storage coefficient of 25%, which is a standard for alluvial aquifers. In areas on the west, north- west of city where groundwater is potable the groundwater table has dried up and the situation is alarming. There is need to rejuvenate such aquifers using artificial recharge techniques to supplement the decreasing natural rainfall recharge using roof water harvesting for sustainable development of the water resources in the city.