MONITORING OF DROUGHT IN QINGHAI PROVINCE BY USING STANDARDIZED PRECIPITATION INDEX (SPI)

1State Key Laboratory of Cryospheric Sciences/Tian Shan Glaciological Station, Northwest Institute of Eco-Environment and Resources, CAS, 320 Donggang West Road, Lanzhou, 730000, China 2University of Khartoum, Faculty of Forestry, Department of Forest Protection and Conservation, Code 13314, Shambat, Sudan 3Northwest Normal University, College of Geography and Environmental Science, Anning Road, Lanzhou 730000, P. R. China 4Division of Hydrology Water-Land Resources, Northwest Institute of Eco-Environment and Resources, CAS, 320 Donggang West Road, Lanzhou, 730000, China


INTRODUCTION
The drought can be defined on the basis of two indicators: (a) environmental indicators (b) water resources indicators (Mawdsley et al., 1994). Drought index is the basis for arid climate research and to measure the extent of the drought in a region (Piara, 2014). Both global climate change and anthropogenic activities are the main driving forces of terrestrial ecosystems (Field, 2001). With the increase in climate warming and intensified anthropogenic activities over the last century (Raupach et al., 2013), socioeconomic drivers are beginning to overwhelm the great forces of nature for some selected processes regionally or even on the global scale (Erb et al., 2009). Drought is among the major meteorological and environmental problems facing humanity . Causes and concepts of climate change divided the theories that explain climate change phenomenon into three categories: extraterrestrial, terrestrial, and oceanic and atmospheric changes (Mustafa 2007). Due to the monsoon climate interacted with the complicated geographical landscapes, severe droughts of high frequency are among the most devastating natural disasters in China. According to statistics, the drought affected areas and drought damaged areas have greatly increased in the past 50 years (Wang et al., 2012). Drought has especially affected the agricultural areas over northern China (Wang et al., 2011). Drought indices are continuous functions of rainfall and/or temperature, river discharge or other measurable hydro-meteorological variables, commonly used to quantify the definition of drought (Thornthwaite, 1948). Effective Drought Index (EDI-Byun) and the Reconnaissance Drought Index RDI (Tsakiris et al., 2007) and Standardized precipitation index (SPI) are commonly used for drought analysis. Among them, SPI is more widely used index because of simple calculation and having multiple time scales (Mckee et al. 1993). The world's arid areas are mainly distributed in most parts of Asia, most of the Australia, most of the Africa, western North America and western South America. Among them China drought is particularly prominent, involving a very wide range, mainly in the north-west and northeast regions. And in China, Qinghai Province, located in the dry arid areas of north-west China, is prominent because of more frequent and severe droughts.

Study area
Qinghai Province has a large variety of ecosystem types, from sub-tropical rain forest in southeast to alpine desert in the north-west. Among all types of land cover vegetation, alpine grassland is the dominant ecosystem, combined cover an area of 715823.8 km 2 , extending from latitude of 31° 40' -39° 30' N and longitude of 89° 25 ' -103° 04' E and altitude 1721 -8500 m ( Figure 1). In addition Table 1 shows the longitude and latitude, altitude and annual precipitation of meteorological stations in Qinghai Province.

Standard Precipitation Index (SPI)
Monthly precipitation records of all available stations in the Qinghai Province were obtained from China meteorological data service (http://data.cma.gov.cn) for the period of 53 years (1961 to 2013). The SPI index was developed by McKee et al. (1993). Details about the SPI index computation can be found in several papers including McKee et al., (1993McKee et al., ( , 1995, Guttman, (1999) and Khalili et al. (2011). SPI is a simple calculation based on the concept that precipitation deficits over varying periods or time scales. SPI index values based on longterm precipitation may change up to 24 months are not reliable (McKee et al., 1993). The index calculation is simple, consider only the precipitation factor, and having multiple time scales, typically have 1, 3, 12, 24, 36 and 48 months equal time scales. Table 2 shows the threshold values of drought for the normal standardized Pa.      1962, 1966-1967, 1970, 1973, 1986, 1992-1993, 1996 and 2001-2004. 24-month shows the high frequency of drought in 1963-1964, 1966-1967, 1970, 1973, 1979-1981, 1992-1993, 1995-1997 and 2002-2004. A 36-month shows a high frequency of drought in 1965-1966, 1969-1971, 1979-1981, 1993, 1996-1998 and 2003-2004. 48month shows a high frequency of drought in 1964-1966, 1970, 1980, 996-1998, 2002-2004. The last eight years (from 2006to 2013 shows no drought condition based on SPI values.  Figure 5 shows the trends of annual SPI in Qinghai Province. The annual-SPI forward curve (UF curve) shows that the drought trend was not significant in the 1960s to the 1990s in Qinghai Province which alternating wet and dry cycles; after the 1990s, drought aggravated north-west of Qinghai Province. The UF curve is 0.05 % significant level line. The annual-SPI UF curve shows that nearly Qinghai Province in 2000s drought trend is not significant, 2004 is the beginning of mutation detection of the humid.

CONCLUSIONS
Drought indices, designed to provide a concise overall picture of droughts, are often derived from massive amounts of hydroclimatic data and are used for making decisions for water resources management and water allocations for mitigating the impact of droughts. In recent years, Qinghai Province is observing intensified climate warming and decrease of precipitation. Frequent trends in arid zone are affecting the region more widely, the economic losses caused by drought is also growing. These situations highlight the need to take comprehensive measures.
This study is focusing in Qinghai Province, using inputs and outputs of SPI index to characterize drought type, severity, and duration, which can assist in identifying appropriate adaptation strategies to minimize the impacts of drought to the agriculture and water sector. This work has a unique contribution for achieving a drought index, which can identify meteorological drought by simply overlaying the maps of the drought index. The use of quantitative SPI for drought management reduces the subjective preferences of decision makers. The SPI is good for the assessment of drought of grassland, wildlife lifethreatening and indirect economic losses of grassland ecosystems far beyond the direct economic loss.
This study recommended adapting and mitigating the drought periods: improving livelihoods, agro-ecosystem resilience, agricultural productivity and the provision of environmental services. In addition, we recommended more additional investigations on crops suitable for the Qinghai Province during drought should be carried out for more accurate information, which can be used for crop modeling of appropriate agricultural and water management during drought. Further studies on drought prediction using future climate scenarios in Qinghai Province, using methods presented in this study, will be part of the future direction of this study.