Search

Key Message: A high-quality rice activation tagging population has been developed and screened for drought-tolerant lines using various water stress assays. One drought-tolerant line activated two rice glutamate receptor-like genes. Transgenic overexpression of the rice glutamate receptor-like genes conferred drought tolerance to rice and Arabidopsis. Rice (Oryza sativa) is a multi-billion dollar crop grown in more than one hundred countries, as well as a useful functional genetic tool for trait discovery. We have developed a population of more than 200,000 activation-tagged rice lines for use in forward genetic screens to identify genes that improve drought tolerance and other traits that improve yield and agronomic productivity. The population has an expected coverage of more than 90 % of rice genes. About 80 % of the lines have a single T-DNA insertion locus and this molecular feature simplifies gene identification. One of the lines identified in our screens, AH01486, exhibits improved drought tolerance. The AH01486 T-DNA locus is located in a region with two glutamate receptor-like genes. Constitutive overexpression of either glutamate receptor-like gene significantly enhances the drought tolerance of rice and Arabidopsis, thus revealing a novel function of this important gene family in plant biology.

Reliable drought prediction is fundamental for water resource managers to develop and implement drought mitigation measures. Considering that drought development is closely related to the spatial-temporal evolution of largescale circulation patterns, we developed a conceptual prediction model of seasonal drought processes based on atmospheric and oceanic standardized anomalies (SAs). Empirical orthogonal function (EOF) analysis is first applied to drought-related SAs at 200 and 500 hPa geopotential height (HGT) and sea surface temperature (SST). Subsequently, SA-based predictors are built based on the spatial pattern of the first EOF modes. This drought prediction model is essentially the synchronous statistical relationship between 90- day-accumulated atmospheric-oceanic SA-based predictors and SPI3 (3-month standardized precipitation index), calibrated using a simple stepwise regression method. Predictor computation is based on forecast atmospheric-oceanic products retrieved from the NCEP Climate Forecast System Version 2 (CFSv2), indicating the lead time of the model depends on that of CFSv2. The model can make seamless drought predictions for operational use after a year-to-year calibration. Model application to four recent severe regional drought processes in China indicates its good performance in predicting seasonal drought development, despite its weakness in predicting drought severity. Overall, the model can be a worthy reference for seasonal water resource management in China. [ABSTRACT FROM AUTHOR]

Each type of drought has different characteristics in different regions. It is important to distinguish different types of droughts and their correlations. Based on gauged precipitation, temperature, simulated soil moisture, and runoff data during the period 1951-2012, the relationships among meteorological, agricultural, and hydrological droughts were analyzed at different time scales in Southwest China. The standardized precipitation evapotranspiration index (SPEI), soil moisture anomaly percentage index (SMAPI), and standardized runoff index (SRI) were used to describe meteorological, agricultural, and hydrological droughts, respectively. The results show that there was a good correlation among the three indices. SMAPI had the best correlation with the 3 month SPEI and SRI values. It indicates that agricultural drought was characterized by a 3-month scale. The three drought indices displayed the similar special features such as drought scope, drought level, and drought center during the extreme drought of 2009-2010. However, the scope and level of SPEI were bigger than those of SMAPI and SRI. The propagation characteristics of the three types of droughts were significantly different. The temporal drought process in typical grids reflect that the meteorological drought occurred ahead of agricultural and hydrological droughts by about 1 and 3 months, respectively. Agricultural drought showed a stable drought process and reasonable time periods for the drought beginning and end. These results showed the quantitative relationships among three types of drought and thus provided an important supporting evidence for regional drought monitoring and strategic decisions. [ABSTRACT FROM AUTHOR]

Climate change is likely to lead to an increased frequency and intensity of extreme weather events, including floods and droughts. Hydrological drought refers to deficiencies in surface and subsurface water supplies and is usually measured by streamflow, and lake, reservoir and ground water levels. Properly assessing hydrological drought is crucial to decision-making and management of regional water resources. In this study, changes in hydrological drought frequency over the Xijiang River Basin in South China are investigated through an analysis of daily streamflow data observed at major hydrological stations along the river during the period 1951-2013. The main results are as follows: (1) Standardized Runoff Drought Index is a suitable measure for regional hydrological drought research in the Xijiang Basin, as its correlation coefficient with actual disaster areas is above 0.6 for Wuzhou hydrological station; (2) the hydrological droughts in the Xijiang Basin typically have a short duration that are often less than 60 days; (3) there were three serious hydrological drought periods (the 1950s to mid-1960s, the late 1980s to mid-1990s and the mid-2000s to early 2010s) and two drought relief periods (the late 1960s to mid-1980s and the late 1990s to early 2000s) for the Xijiang Basin; (4) hydrological droughts in the Xijiang River occur frequently and are mainly concentrated in summer and spring, although serious hydrological droughts can easily arise in autumn. Droughts tend to be more frequent but less severe moving from upstream to downstream, and a long duration often accompanies high severity for a single drought event; and (5) severe hydrological droughts in upstream and midstream areas are characterized by long durations and high severities, respectively. Return periods based on copula could generally reflect actual drought situations, and severe and extreme hydrological droughts occur when return periods greater than 20 and 50 a, respectively. [ABSTRACT FROM AUTHOR]

The general approach to drought regionalisation regards the multi-year average values of drought indexes as regionalisation indicators, without taking long-term variability into account. This type of regionalisation is known as static regionalisation, or mean regionalisation, and does not consider possible variations over multiple years. In order to analyse the probability of climate aridity and drought, in this study, we firstly introduce the novel concept of a probabilistic aridity index for climate regionalisation and a drought index for drought risk regionalisation, as well as a methodology for estimating the frequency of the probabilistic aridity and drought index. Details of the approach used in the regionalisation of aridity and drought risk, and its associated characteristics, are then discussed. Finally, the value of our approach is demonstrated in China. The result shows that climate and drought risk regionalisation is able to provide enriched aridity and drought probability information compared with general climate and drought regionalisation, and can thus provide enhanced technical support for the rational allocation of water resources and the prevention and mitigation of drought disasters. [ABSTRACT FROM AUTHOR]

The Xijiang River is known as the Golden Watercourse because of its role in the development of the Pearl River Delta Regional Economic System in China, which was made possible by its abundant water resources. At present, the hydrological regime of the Xijiang River has now become complicated, the water shortages and successive droughts pose a threat to regional economic development. However, the complexity of hydroclimatological processes with emphasizes on drought has not been comprehended. In order to effectively predict and develop the adaptation strategies to cope with the water scarcity damage caused by hydrological droughts, it is essential to thoroughly analyze the relationship between hydrological droughts and pre/post-dependent hydroclimatological factors. To accomplish this, the extreme-point symmetric mode decomposition method (ESMD) was utilized to reveal the periodic variation in hydrological droughts that is characterized by the Standardized Drought Index (SDI). In addition, the cross-wavelet transform method was applied to investigate the correlation between large-scale climate indices and drought. The results showed that hydrological drought had the most significant response to spring ENSO (El Niño-Southern Oscillation), and the response lags in sub-basins were mostly 8–9 months except that in Yujiang River were mainly 5 or 8 months. Signal reservoir operation in the Yujiang River reduced drought severity by 52–95.8% from January to April over the 2003–2014 time period. Similarly, the cascade reservoir alleviated winter and spring droughts in the Hongshuihe River Basin. However, autumn drought was aggravated with severity increased by 41.9% in September and by 160.9% in October, so that the land surface models without considering human intervention must be used with caution in the hydrological simulation. The response lags of the VCI (Vegetation Condition Index) to hydrological drought were different in the sub-basins. The response lag for the Hongshuihe, Yujiang, and Liujiang River Basins were mostly 0–4 months, 0–1 months, and 2–3 months, respectively, but there was no obvious regular change pattern in the Guijiang River Basin. [ABSTRACT FROM AUTHOR]