CLIMATE RESEARCH AND SERVICES INDIA METEOROLOGICAL DEPARTMENT MINISTRY OF EARTH SCIENCES PUNE Observed Rainfall Variability and Changes over Telangana State Met Monograph No.: ESSO/IMD/HS/Rainfall Variability/25(2020)/49 Pulak Guhathakurta, Sakharam Sanap, Preetha Menon Ashwini Kumar Prasad, S T Sable and S C Advani GOVERNMENT OF INDIA MINISTRY OF EARTH SCIENCES INDIA METEOROLOGICAL DEPARTMENT Met Monograph No.: ESSO/IMD/HS/Rainfall Variability/25(2020)/49 Observed Rainfall Variability and Changes Over Telangana State Pulak Guhathakurta, Sakharam Sanap, Preetha Menon, Ashwini Kumar Prasad, S.T. Sable and S C Advani INDIA METEOROLOGICAL DEPARTMENT PUNE - 411005 1 DOCUMENT AND DATA CONTROL SHEET 1 Document Title Observed Rainfall Variability and Changes Over Telangana State 2 Issue No. ESSO/IMD/HS/Rainfall Variability/25(2020)/49 3 Issue Date January 2020 4 Security Classification Unclassified 5 Control Status Uncontrolled 6 Document Type Scientific Publication 7 No. of Pages 23 8 No. of Figures 42 9 No. of References 3 10 Distribution Unrestricted 11 Language English 12 Authors Pulak Guhathakurta, Sakharam Sanap, Preetha Menon, Ashwini Kumar Prasad, S.T. Sable and S C Advani 13 Originating Division/ Climate Research Division/ Climate Application & Group User Interface Group/ Hydrometeorology 14 Reviewing and Director General of Meteorology, India Approving Authority Meteorological Department, New Delhi 15 End users Central and State Ministries of Water resources, agriculture and civic bodies, Science and Technology, Disaster Management Agencies, Planning Commission of India 16 Abstract India is in the tropical monsoon zone and receives plenty of rainfall as most of the annual rainfall during the monsoon season every year. However, the rainfall is having high temporal and spatial variability and due to the impact of climate changes there are significant changes in the mean rainfall pattern and their variability as well as in the intensity and frequencies of extreme rainfall events. The report brings the result of the analysis based on the recent 30 years of data (1989- 2018) on the mean spatial rainfall pattern as well as mean spatial pattern of different rainfall events, trends and variability as well as extreme rainfall events during the monsoon months and annual for the state. 17 Key Words Rainfall trend, variability, extreme events, dry days 2 1. Introduction Telangana state is the 29th state of India and came into existence on 2 June 2014 and it is bifurcated from Andhra Pradesh. It is located between 15°55’ N to 19°55’ N latitude and 77°10’ E to 81°50’ E longitude in south central India and it shares its boundaries with Andhra Pradesh to the south and southeast, Chhattisgarh and Orissa to the northeast, Maharashtra to the north and west and Karnataka to the west. The state of Telangana has geographical area about 114,840 sq km. Telangana is situated on the Deccan plateau, in the central stretch of the eastern seaboard of the Indian peninsula. The average elevation of the plateau area is about 500 meter, higher in west and southwest and sloping downward toward the east and northeast, where it meets the discontinuous line of the Eastern Ghats ranges. Western part of the state is mostly hilly with an altitude generally varies from 300m to 600m and some part is having an altitude of 600 m to 1361 m. Peak height of the state is 1361 m which is observed in the extreme eastern part of the state. Fig.1 gives the location of the districts of the state. Fig. 1 District wise map of the Telangana state Many studies available on the observed trends and variability of rainfall and also extreme rainfall events over India, but all the studies are based on past 100 years or more data and also the recent years are not included (Guhathakurta et al, 2015; Guhathakurta et al, 2011; Guhathakurta & Rajeevan, 2008 etc). Also, there are limited studies on district rainfall trends and variability of Telangana state. In the present report all the analysis of observed rainfall patterns, trends and variability have been done based on recent 3 past 30 years (1989-2018) that will help to have idea of the recent changes for climate change adaptation and management by the state authorities. 2. Data and Methodology Daily Rainfall data from 1989 to 2018 is considered for the analysis of trend variability and mean rainfall patterns. From the daily rainfall data monthly rainfall series of each stations are computed. Monthly district rainfall series has been constructed by considering arithmetic average of all the station rainfall values within the district. The monthly rainfall series of the state has been computed by using area weighted rainfall values of all the districts within the state. The objective of the analysis is to: 1. Identify the spatial pattern of the mean rainfall 2. Understand district wise observed rainfall trend and variability in annual and SW monsoon season (June, July, august and September). Daily station rainfall data is utilized for identification of the mean spatial patterns and rainfall intensity trends. From mean and standard deviation (SD), the coefficient of variation (CV) is calculated as follows: Standard Deviation Coeffcient of variation (CV) = × 100 Mean 3. State rainfall mean and variability and trend Mean rainfall (mm) and CV for the monsoon months (June, July, August and September), southwest monsoon season and annual for the period 1989-2018 is shown in Table 1. Highest contribution to the SW monsoon rainfall is coming from the month of August (30.5 %) followed by July (29.7%), September (21.2 %) and June (18.6 %) respectively. Telangana state receives 78.8 % of the annual rainfall merely from SW monsoon season. The CV of monsoon and annual rainfall for Telangana state is 22.5 % and 20.5 % respectively. June July August September JJAS Annual Mean 132.7 211.5 217.6 151.4 713.2 905.1 CV 41.3 44.8 34.8 43.2 22.5 20.5 Table 1 Mean rainfall (mm) and coefficient of variation for the monsoon months, southwest monsoon season and annual 4 Fig. 2 and 3 depicts the time series of rainfall (mm) for the months of June, July, August, September, southwest monsoon season and annual respectively. The trend lines are also displayed for each of the series. Analysis indicates that neither monthly rainfall nor seasonal or annual rainfall show any significant increasing/decreasing trend. Monthly rainfall for the months of June, July and August show the decreasing trend while September show slight upward trend, however it is statistically insignificant. Both seasonal and annual rainfall show decreasing trend (statistically insignificant). Fig. 2 Time series of rainfall in mm for the months of June, July, August, September and trends 5 Fig. 3 Time series of rainfall in mm for the southwest monsoon season and annual trends Highest rainfall occurred in last 30 (1989-2018) years for each monsoon month, SW monsoon season and annual is shown in Table 2. Month/Season/Annual Highest rainfall received (mm) Year June 234.8 2000 July 492.6 2013 August 426.5 1990 September 248.7 2007 JJAS 1133.1 2013 Annual 1384.7 2013 Table 2. Highest rainfall records for SW monsoon months, SW monsoon season and annual. 4. District rainfall mean, variability and trend 4.1 Mean and coefficient of variation Rainfall statistics for the districts of Telangana for SW monsoon months, SW monsoon season and annual is presented in Table 3. The spatial pattern of rainfall statistics is depicted in Figure 4 and 5. Districts from Northern and Eastern region of the Telangana receives highest amount of rainfall in June, July, August, September and SW monsoon season. It is in the range of 189-216 mm for June, 283-398 mm for July, 290-401 mm for August, 141-179 mm in September, 850-1151 mm for SW monsoon season and 863- 1400mm for annual respectively. Mean spatial pattern of rainfall also indicate that northern districts receive highest rainfall in June and eastern region records highest amount of rainfall for other timescales. Central 6 and southern region of the Telangana receives less rainfall compare to northern and eastern region of the state. It ranges from 80-135 mm in June, 111-226 mm in July, 124-235 mm in August, 83-122 mm in September, 398-700 mm in SW monsoon season and 530-863 mm in annual. JUNE JULY AUGUST SEPTEMBER MONSOON ANNUAL DISTRICT MEA N CV MEAN CV MEAN CV MEAN CV MEAN CV MEAN CV ADILABAD 193.1 122 274.9 42 304.5 89 152.4 145 924.9 44 1090.7 54 HYDERABAD 105.9 52 167.3 56 204.0 48 134.3 58 611.5 25 827.2 60 KARIMNAGAR 134.7 161 221.6 46 213.6 45 148.4 62 718.3 51 881.9 59 KHAMMAM 159.5 142 281.3 95 286.6 89 179.2 132 906.6 46 1143.2 42 MAHBUBNAGAR 90.8 228 128.0 54 133.7 159 129.3 166 481.7 63 662.1 98 MEDAK 111.1 258 175.7 134 192.5 121 132.2 170 611.5 71 780.2 62 NALGONDA 89.6 232 127.6 173 146.1 151 141.4 160 504.8 61 703.3 106 NIZAMABAD 160.2 143 251.1 46 263.4 52 141.2 163 815.9 50 987.2 46 RANGAREDDY 108.6 47 151.6 51 178.1 43 149.3 45 587.5 25 786.8 118 WARANGAL 148.2 149 252.5 43 237.9 103 161.6 56 800.2 61 992.3 87 B.KOTHAGUDEM 160.0 295 325.0 166 296.2 180 158.1 297 939.4 85 1179.0 76 JAGTIAL 193.4 255 265.1 194 272.7 194 134.9 342 866.1 89 1099.0 72 JANGAON 132.8 347 200.5 246 178.7 269 133.2 345 645.2 106 851.2 111 J.BHUPALPALLY 188.4 257 397.7 144 400.7 146 164.1 290 1150.9 77 1358.6 71 JOGULAMBA GADWAL 80.2 548 110.7 407 124.3 407 83.3 526 398.5 157 532.1 150 KAMAREDDY 166.0 287 241.0 211 310.5 175 101.7 440 819.2 93 1041.7 83 KOMARAM BHEEM 196.8 251 327.4 169 326.9 169 159.3 297 1010.5 87 1225.8 69 MAHABUBABAD 156.9 301 268.3 193 283.0 185 170.3