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Journal of Arid Land  2021, Vol. 13 Issue (5): 433-454    DOI: 10.1007/s40333-021-0065-6
Research article     
Spatiotemporal analysis of drought variability based on the standardized precipitation evapotranspiration index in the Koshi River Basin, Nepal
Nirmal M DAHAL1,2, XIONG Donghong1,3,4,*(), Nilhari NEUPANE5, Belayneh YIGEZ1,2, ZHANG Baojun1,3,4, YUAN Yong1,2, Saroj KOIRALA1,2, LIU Lin1,2, FANG Yiping1
1Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China
2University of Chinese Academy of Sciences, Beijing 100049, China
3Branch of Sustainable Mountain Development, Kathmandu Center for Research and Education, CAS-TU, Kathmandu 44600, Nepal
4Sino-Nepal Joint Research Centre for Geography, IMHE-TU-YNU, Kathmandu 44600, Nepal
5International Centre for Integrated Mountain Development (ICIMOD), Lalitpur, GPO 3226, Nepal
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Drought is an inevitable condition with negative impacts in the agricultural and climatic sectors, especially in developing countries. This study attempts to examine the spatial and temporal characteristics of drought and its trends in the Koshi River Basin (KRB) in Nepal, using the standardized precipitation evapotranspiration index (SPEI) over the period from 1987 to 2017. The Mann-Kendall test was used to explore the trends of the SPEI values. The study illustrated the increasing annual and seasonal drought trends in the KRB over the study period. Spatially, the hill region of the KRB showed substantial increasing drought trends at the annual and seasonal scales, especially in summer and winter. The mountain region also showed a significant increasing drought trend in winter. The drought characteristic analysis indicated that the maximum duration, intensity, and severity of drought events were observed in the KRB after 2000. The Terai region presented the highest drought frequency and intensity, while the hill region presented the longest maximum drought duration. Moreover, the spatial extent of drought showed a significant increasing trend in the hill region at the monthly (drought station proportion of 7.6%/10a in August), seasonal (drought station proportion of 7.2%/10a in summer), and annual (drought station proportion of 6.7%/10a) scales. The findings of this study can assist local governments, planners, and project implementers in understanding drought and developing appropriate mitigation strategies to cope with its impacts.

Key wordsdrought duration      drought intensity      drought severity      standardized precipitation evapotranspiration index      mountains      hills      Terai     
Received: 01 June 2020      Published: 10 May 2021
Corresponding Authors: XIONG Donghong     E-mail:
About author: *XIONG Donghong (E-mail:
Cite this article:

Nirmal M DAHAL, XIONG Donghong, Nilhari NEUPANE, Belayneh YIGEZ, ZHANG Baojun, YUAN Yong, Saroj KOIRALA, LIU Lin, FANG Yiping. Spatiotemporal analysis of drought variability based on the standardized precipitation evapotranspiration index in the Koshi River Basin, Nepal. Journal of Arid Land, 2021, 13(5): 433-454.

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Fig. 1 Overview of the Koshi River Basin (KRB), Nepal (a) as well as the distributions of weather stations in the KRB (b)
Region Annual mean minimum temperature (°C) Annual mean maximum temperature (°C) Annual precipitation (mm) Climate Elevation (m)
Mountain 11.3 22.3 1953.5 Cool temperate to alpine >2000
Hill 13.0 24.2 1641.4 Subtropical to warm temperate 300-2000
Terai 19.2 30.6 1637.2 Tropical <300
Table 1 Major climate features of the mountain, hill and Terai regions (derived from the selected districts) of the Koshi River Basin (KRB), Nepal
Region District Station name Elevation (m) AMP (mm) CV-AMP (%) PET (mm) CV-PET (%)
Mountain Dolakha Jiri 1877 2441.4 10.3 1222.3 2.3
Sankhuwasabha Chainpur 1277 1444.2 14.3 1367.8 4.7
Taplejung Taplejung 1744 1974.9 13.2 1161.3 4.3
Hill Kathmandu Panipokhari 1329 1504.9 13.2 1449.1 6.1
Kathmandu Kathmandu Airport 1337 1480.4 14.8 1476.0 2.6
Lalitpur Khumaltar 1334 1163.4 16.7 1394.6 2.4
Lalitpur Godavari 1527 1708.6 18.0 1273.1 6.3
Bhaktapur Nagarkot 2147 1863.3 14.4 1129.7 9.3
Makwanpur Hetauda 452 2365.3 17.9 1607.6 3.8
Kavre Dhulikhel 1543 1483.1 18.8 1230.6 8.0
Kavre Panchkhal 857 1121.9 17.6 1621.1 2.8
Okhaldhunga Okhaldhunga 1731 1781.4 11.4 1185.4 7.3
Dhankuta Pakhribas 1720 1530.5 12.4 1110.1 2.5
Dhankuta Dhankuta 1192 967.0 19.9 1261.1 9.8
Terai Bara Simara 137 1814.7 22.0 1609.1 2.9
Bara Parwanipur 87 1591.9 21.8 1599.3 3.5
Sarlahi Karmaiya 139 1834.0 20.3 1549.3 2.8
Sarlahi Manusmara 90 1438.8 30.2 1608.5 2.8
Dhanusa Janakpur 76 1523.2 26.8 1540.5 2.7
Siraha Lahan 110 1368.1 22.5 1485.2 12.4
Saptari Rajbiraj 68 1500.0 26.4 1601.8 5.5
Saptari Phattepur 83 1731.6 23.9 1693.5 4.5
Sunsari Tarahara 120 1976.1 17.6 1553.3 2.7
Table 2 Details of the weather stations selected from different regions in the KRB, Nepal
SPEI value Category
≥ -0.99 Near normal
-1.49- -1.00 Moderate drought
-1.99- -1.50 Severe drought
≤ -2.00 Extreme drought
Table 3 Classification of drought based on the standardized precipitation evapotranspiration index (SPEI) values
Fig. 2 Annual variation of the standardized precipitation evapotranspiration index (SPEI) values at the 12-month time scale at the regional (a-c) and basin (d) levels of the KRB from 1987 to 2017. The trend of the SPEI per decade (Mann-Kendall test) and the statistical level of significance are also shown.
Fig. 3 Seasonal variation in the SPEI values at the 3-month time scale at the regional (a-f) and basin (g and h) levels of the KRB from 1987 to 2017. The trend of the SPEI per decade (Mann-Kendall test) and the statistical level of significance are also shown. NS, not significant.
Region Maximum drought
Duration (month) Starting-ending time Severity Starting-ending time Intensity Starting-ending time
Mountain 14.0 Apr 2005-May 2006
Feb 2012-Mar 2013
15.49 Apr 2005-May 2006 1.74 Jun 2009-Nov 2009
Hill 17.0 Dec 2007-Apr 2009 15.72 Dec 2007-Apr 2009 1.39 Jan 2006-Mar 2006
Terai 16.0 Apr 1994-Jul 1995 17.28 Apr 1994-Jul 1995 1.84 Nov 2005
KRB 15.0 Jan 2009-Aug 2010 16.05 Feb 2012-Mar 2013 1.59 Jan 2006-Mar 2006
Region Average drought Drought frequency
Duration (month) Severity Intensity
Mountain 5.7 5.37 0.94 74
Hill 5.9 5.60 0.94 77
Terai 4.7 4.77 1.01 81
KRB 5.8 5.80 1.00 71
Table 4 Summary of the duration, severity, and intensity of drought events identified from the SPEI values at the 3-month time scale from 1987 to 2017 at the regional and basin levels of the KRB
Time M-K trend in drought station proportion (%/10a)
Mountains Hills Terai KRB
January 0.0 5.3* 0.0 2.2
February 0.0 0.0 0.0 2.9*
March 0.0 3.0* 0.0 0.0
April 0.0 0.0 0.0 0.0
May 0.0 0.0 0.0 0.0
June 0.0 0.0 -4.8* 0.0
July 0.0 5.1* 0.0 3.3
August 0.0 7.6* 0.0 5.7*
September 0.0 7.0** 0.0 4.8*
October 0.0 0.0 0.0 3.3
November 0.0 0.0 0.0 2.9
December 0.0 0.0 0.0 0.0
Spring 0.0 3.0 1.6 0.7
Summer 4.1 7.2* 0.0 3.8
Autumn 0.0 4.5* -2.5 4.6
Winter 0.0 5.7* -1.4 3.9
Annual 5.8* 6.7** 0.0 4.2*
Table 5 Mann-Kendall (M-K) trends in drought station proportion series calculated from the SPEI values at the 3-month time scale at the regional and basin levels of the KRB from 1987 to 2017
Region Climate variable Season Annual
Spring Summer Autumn Winter
Mountain Precipitation (mm/a) -6.40 -7.70 4.80 -11.70* -25.10
Temperature (°C/a) 0.20 0.10 0.10 0.30 0.20
Hill Precipitation (mm/a) 1.70 -68.30 -0.40 -10.90* -84.40*
Temperature (°C/a) 0.50** 0.40** 0.30** 0.50*** 0.40***
Terai Precipitation (mm/a) 11.80 -59.60 -13.40 -8.00* -59.00
Temperature (°C/a) 0.20 0.20** 0.10 0.03 0.10
KRB Precipitation (mm/a) 2.20 -64.00 -12.50 -10.50* -60.60
Temperature (°C/a) 0.30** 0.30*** 0.20** 0.20* 0.30***
Table 6 M-K trends of seasonal and annual precipitation and temperature at the regional and basin levels of the KRB from 1987 to 2017
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