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The calculation formulas are as follows: Models perform better with higher. This research assumes that the GCM with the highest is the relative optimal model and projects future changes in drought with the output of the relative optimal model. Figures 8 a and 8 b show the time series of crop evapotranspiration and effective precipitation. It could be found that there was a negative trend in the MLJRB during the last 50 years with the average annual decreasing rate of 1.
But the trend did not pass the significance test through Mann-Kendall test Figure 8 a. From the perspective of spatial variety, crop evapotranspiration in the area of Yibin, Panzhihua, Kunming, and Yuxi showed a decreasing trend, while it has been increased in Zhongdian, Xichang, and Lijiang Figure 9 a.
The effective precipitation has decreased by 8. The break points of the annual effective precipitation tested by the Mann-Kendall method were in the beginning of the s and the late of the s. Annual effective precipitation during to was From autumn in to spring in , southwest China endured a severe drought episode. From October to February , the extreme drought area traveled north-south- north, occurring in Chuxiong, Kunming, Yuxi, Yinbin, and Zhaotong.
After February , the drought was gradually relieved.
Deciles, Standardized Precipitation and Reconnaissance Drought Indices have been used to assess the meteorological drought in the world and they show their performance, why they have been chosen to study Wadi Djelfa-Hadjia sub-basin. The first step includes the normalization of the SPI index according to the relative average precipitation, based on a set of coefficients a i , b i that satisfy:. A representative station Kalives, RCP4. No citations found yet 0. Equation 4 provides a simple measure of the water surplus or deficit for the month. View at Google Scholar Q. Author links open overlay panel N.
Overall, the spatial distribution of drought assessment was consistent with documented real drought. There exist some discrepancies in drought assessment. The reason of the disagreement was that the winter wheat was just sowed or has not yet been sowed during this period. Less water was required and the winter wheat was less sensitive to water deficit. Mainly it was because the winter wheat had been undergoing a period of tillering-jointing.
More water was required and the winter wheat was sensitive to water deficit. The temporal variation of drought area was analyzed with SSDI12 the time scale was 12 month from to Figure 12 , which showed that the drought had obviously interannual and fluctuation in the MLJRB. The average drought area was 5.
From the s to the late s, the drought exhibited a significant decreased trend. Compared with to , the drought area during to decreased by But the drought area increased rapidly again after The drought area during to reached up to 9. These results imply that the northeast and south regions of the study area were prone to drought. Panzhihua, Xichang, and Chuxiong show higher drought durations, with total DD commonly reaching month or more Figure 13 b. Panzhihua, Dali, Chuxiong, and Yuxi suffered from more severe drought. The absolute value of DS was more than Figure 13 c.
These regions should cultivate drought-resistant crops and construct water saving irrigation project. Presented in Figure 15 a is the geographic distribution of change in crop evapotranspiration, in terms of relative optimal model in the projection period to compared to the baseline period — The dominant feature in the projection period is an overall increase in crop evapotranspiration across the MLJRB.
The crop evapotranspiration is predicted to increase by 7.
Future changes in effective precipitation, another important determinant of drought besides crop evapotranspiration, are highlighted in Figure 15 b. Widespread decreases in effective precipitation cover the whole region throughout the projection period. However, the change is not very noticeable.
The effective precipitation is predicted to decrease by 3. Using the crop evapotranspiration and effective precipitation of relative optimal models under RCP4. Figure 16 shows the change in drought area from — to — It could be related to the less increase of crop evapotranspiration and relatively pronounced increase of effective precipitation. But under current climate conditions, more drought events and longer duration mainly occur in these regions compared with the north or west of the MLJRB.
That is, the spatial pattern of the drought characteristics may change under future climate conditions. The variability and pattern of the drought characteristics are one of the most important aspects of drought disaster mitigation. Based on monthly or annual standardized supply-demand water index, in this study, we used drought area, times, duration, and severity as the main assessing indicators and investigated the spatial-temporal characteristics of drought in the middle and lower Jinsha river basin MLJRB.
The following conclusions are drawn from this study.
We have described a drought index the standardized supply-demand water index SSDI that uses crop evapotranspiration and effective precipitation and it is based on a normalization of the simple water balance. The spatial distribution of drought assessment was consistent with documented real drought.
We also assessed the properties and advantages of this index in comparison to the two most widely used drought indices: The results showed that the SSDI can express the sensibility of crop to water deficit. For the period to , the average drought area was 5.
The pattern for the drought characteristics indicated that the region for greater drought severity with more drought events and longer duration was mainly distributed in Dali, Chuxiong, Kunming, and Yuxi. Under future climate condition, the crop evapotranspiration is projected to increase while the effective precipitation will change slightly.
That is, the water deficit will exacerbate in the future.
For the period to , an increase of total drought area by The projection also gives an increase of severe drought area by Compared to the reference period — , the MLJRB is likely to experience more widespread drought in the future. We can conclude that the spatial pattern of the drought characteristics may change under future climate conditions. Create a SciFeed alert for new publications With following keywords hydrological drought.
By following author Charles Onyutha. One email with all search results. One email for each search. Hydrology , 4 4 , 48; https: Faculty of Technoscience, Muni University, P. Box , Arua, Uganda. The dotted line is a linear trend. The horizontal axis is based on logarithmic scale. The horizontal axis of each chart is based on logarithmic scale. In the legend, e. One email for each search. Sustainability , 10 6 , ; https: Abstract Severe droughts have occurred in East Asia; however, observational hydroclimate data that covers the entire region is lacking.
The objective of this study is to investigate drought assessment in East Asia. This study classified drought frequency into four classes depending on the drought severity with 5-deg gapped longitude and latitude for — in East Asia and found that moderately dry D2 and severely dry D3 drought frequency classes matched well between the CLM and CRU data. Furthermore, this study suggests the possibility of CLM application to other regions to generate hydroclimate data that is otherwise insufficient.
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