Journal of Water Resource Research and Development Volume 2 Issue 2 Assessment of Meteorological Drought in Anantapur District (Andhra Pradesh) Athira K.* Assistant Professor, Department of Civil Engineering, Vimal Jyothi Engineering College, Kannur, Kerala, India. *Corresponding Author E-Mail Id:[email protected] ABSTRACT Droughts are serious extreme events that have adverse effects on the physical environment and water resource systems in both developed and developing countries. In India, over 68% of the area is drought affected, Anantapur is one such district where drought condition is prevailing for several years and its effects are severely visible in all sectors. In this study, a non-parametric test (Mann Kendall test) was used to check monotonic trend in each grid level and magnitude was calculated by Sen’s slope test. The effect of meteorological parameters like precipitation and temperature assessed through a drought index called standardized precipitation- evapotranspiration index (SPEI) for a period of 1971-2003 and its spatial distribution also estimated. Studies show that the intensity and frequency of drought has increased during the same period. Keywords:-Meteorological drought, Trend test, SPEI INTRODUCTION where drought conditions are prevailing Drought occurs virtually in all climatic consistently over many years causing regimes, and it can be defined as a severe stress to the local economy, prolonged period of abnormally low especially the agriculture [6]. precipitation, unlike other hazards the footprints of drought is typically larger, Drought indices are typically computed which affects all sectors. In India, numerical representations of drought drought has resulted in millions of deaths severity, assessed using climatic or hydro- over the course of the 18th, 19th, and 20th meteorological inputs. In the last few centuries. Failure of monsoon is the main decades, lots of drought indices have been reason of drought in India, it causes below developed, each index are specifically for average crop yield and it adversely affects particular climatic conditions. Recently the social and economic condition. This is developed drought index, standardized particularly true of major drought-prone precipitation- evapotranspiration index regions such as Andhra Pradesh southern (SPEI) is incorporate the effect of and eastern Maharashtra, northern precipitation and temperature so it can be Karnataka, Odisha, Gujarat, Telangana and taken as a better approach to express the Rajasthan. Drought indices and indicators climate change in the drought scenario. In are mainly used to track drought this paper, characterizing effect of climate conditions result depend upon the region change in the Anantapur district was and climate conditions. Drought is a studied and drought distribution mapped. recurrent phenomenon in India. About 107 million hectares of the country i.e., over 68 percent of India, spread over several DATA AND METHODS administrative districts in many states, is Study Area affected by drought. Anantapur is one such Anantapur District district of Andhra Pradesh (AP) State Anantapur district is one of the four HBRP Publication Page 1-8 2019. All Rights Reserved Page 1 Journal of Water Resource Research and Development Volume 2 Issue 2 districts of Rayalaseema Region and the September. September and October are the largest among the 13 districts of Andhra wettest months of the year. The mean Pradesh. The district is economically seasonal rainfall distribution is 316 mm backward and chronically drought during south-west monsoon (June- affected. The district lies between North September) 146 mm during north-east latitudes 13° 40’ and 16° 15’ and between monsoon (Oct-Dec). The summer season East longitudes 70° 50’ and 78° 38’. The continues from March to May, when the geographical area of the district is 19,197 temperature rises to a maximum of 40°C sq.km with a population of 40.83 lakhs. and goes down to the minimum of 23°C. The population density, which was 54 In this study, 9 grids of .5*.5 degree persons per sq.km during 1901, has risen resolution is selected within the district to 213 persons per sq.km as per 2011 boundary. Latitude and longitude of each census. grids are [14°, 77°], [14°, 77.5°], [14°, 78°], [14.5°, 77°], [14.5°, 77.5°], [14.5°, The average annual rainfall of the district 78°], [15°, 77°], [15°, 77.5°], [15°, 78°]. is 535 mm, which ranges from nil rainfall The location of the grids in the map is in February and March to 129 mm in given in the Figure1. Fig.1: Location of 0.50 x0.50 grid points in the Anantapur district HBRP Publication Page 1-8 2019. All Rights Reserved Page 2 Journal of Water Resource Research and Development Volume 2 Issue 2 Data Processing to calculate SPEI. With a value for PET, Standardized Precipitation- the difference between the precipitation Evapotranspiration Index (SPEI) is used (P) and PET for the month i calculated for the drought assessment. It required (Di): monthly precipitation and temperature data Di = Pi-PETi as input. 0.5*0.5 degree gridded daily precipitation data and 1*1 degree gridded Where Pi is the monthly precipitation temperature data from Indian (mm) and PETi (mm) is calculated Meteorological Department (IMD) for the according to the method of Penman- period of 1971-2003 (33 years) are used Monteith or Hargreaves or Thornthwaite for the study. Data is given in ASCII based on the availability of data. The format and c programming was used to calculated D values were aggregated at extract the data. Linear interpolation various time scales: applied for re-gridding the temperature ∑ Pn-t –PETn –t , n ≥ k data and converted to 0.5 * 0.5 resolution. Where k (months) is the time scale of the Monthly precipitation and temperature aggregation and n is the calculation were calculated. number. The D values are undefined for k >n. A log-logistic probability distribution Trend Analysis function was fitted to the data series of D, Statistical trend in annual meteorological as it adapts very well to all time scales. data was analyzed using non parametric Mann Kendall (MK) test The it has been Mapping used by a number of researchers [3,5,7,8] Different techniques can be used to to verify the presence of statistically generate a continuous map of significant trend in meteorological meteorological drought. One such variables, such as precipitation, technique generates an interpolated surface temperature and streamflow, with of estimated values at locations between reference to climate change. MK test sites based on mathematical relationships checks the existence of a positive or of the indicator or index between the negative trend in the time series and the original point data. Often this produces a magnitude of the trend was determined by map that appears “natural”, but is still Sen’s slope estimator. Trend analysis for based on the data from specific points and precipitation and temperature was carried is only as accurate as the original data and out at a significance limit, α= .05 for nine the interpolation technique. No single grids. interpolation method can be applied to all situations, and the most commonly used Calculation of SPEI interpolation techniques include Kriging, The Standardized Precipitation Spline, and Inverse Distance Weighting Evapotranspiration Index (SPEI) is an (IDW). extension of the widely used Standardized Precipitation Index (SPI). The SPEI is Each interpolation technique has its designed to take into account both advantages and disadvantages. Some precipitation and potential techniques are more exact than others, but evapotranspiration (PET) in determining take longer to produce the desired output. drought. Thus, unlike the SPI, the SPEI The Kriging method has geological captures the main impact of increased applications and also applicable in the temperatures on water demand. This mining industry, assumes that there is a represented simple water balance which relationship between points that is non- was calculated at 1, 3, 6, 9, 12 time steps random and changes over space. The HBRP Publication Page 1-8 2019. All Rights Reserved Page 3 Journal of Water Resource Research and Development Volume 2 Issue 2 Spline method is used when minimizing The data, as the name implies, are the overall surface curvature is important. weighted to favor data closer in proximity Inverse Distance Weighting (IDW) is used to the point being processed. IDW was when the data points are scattered but used for this drought mapping, because dense enough to represent local variations. gridded data set was adequately dense [3]. RESULTS AND DISCUSSION 1200 1000 800 600 400 PRECIPITATION IN MM IN PRECIPITATION 200 0 1970 1975 1980 1985 YEARS 1990 1995 2000 2005 grid1 grid2 grid3 grid4 grid5 grid6 grid7 grid8 grid9 Fig.2: Gridded annual precipitation in Anantapur district (1971-2003) 29.00 28.50 28.00 27.50 27.00 26.50 26.00 temperature in in 0C temperature 25.50 25.00 24.50 24.00 1975 1982 1989 1996 1971 1972 1973 1974 1976 1977 1978 1979 1980 1981 1983 1984 1985 1986 1987 1988 1990 1991 1992 1993 1994 1995 1997 1998 1999 2000 2001 2002 2003 year grid1 grid2 grid3 grid4 grid5 grid6 grid7 grid8 grid9 Fig.3: Gridded annual temperature in Anantapur district (1971-2003) Trends in Precipitation and (Ha), i.e. monotonic trend exists in the Temperature Data long-term precipitation data. From Sen’s MK test rejected the null hypothesis (H˳) slope test, 8 grids are showing a negative and accepted the alternative hypothesis trend and only one grid having a positive HBRP Publication Page 1-8 2019. All Rights Reserved Page 4 Journal of Water Resource Research and Development Volume 2 Issue 2 trend with magnitude .49mm/year in the table1. This decrease in precipitation and case of temperature all grids showing a increase in temperature are the main positive trend with an average magnitude reason behind the persistent drought .01210C/year and result are given in the condition in Anantapur district.