Concurrent and lagged relationships among various drought indices in the United states

The purpose of this study is to examine the nature of the concurrent and lagged relationships among various drought type-specific measures of drought severity. Monthly values of average temperature (TEMPZ), total precipitation (PREZ), the Palmer moisture anomaly index (ZINX) the Palmer drought severity index (PDSl), and the Palmer hydrologic drought seventy Index (PHDI) were examined from a sample of climatic divisions, in the United States for the period,1931-1985. The relationships are examined at two levels through the use of simple correlations. Level one utilizes data from the entire study period. Data from selected drought events are employed in level two. The results show that the strongest relationships are between drought indices with similar rates of response to changes in moisture supply and demand. The correlations also show that lagged values of fast-response drought indices (ZINX, PREZ) arc more strongly correlated with the slow-response PHD1 than concurrent values. Intersite differences between correlated pairs of indices are generally small and follow consistent trends; cross the flow pattern sample for both level one and level two analyses. Intra-site differences are large for some pairs of correlated indices indicating that characteristics of individual droughts can deviate substantially from average or normal conditions

Study on the driven mechanism of hydrologic drought based on the lithology-combined structure of the Karst drainage basin in South China

Hydrologic drought, considered as a typical natural phenomenon in the background of global climate changes, is the continuation and development of meteorological and agricultural droughts, and is the ultimate and most thoroughly drought. The research area controlled by the 55 hydrological sections in South China is selected in this paper, and the intensity and frequency of hydrologic droughts are analyzed by the Standardized Runoff Index (SRI), and the driven mechanism of watershed lithologies to hydrologic droughts is discussed. The results show that (i) the hydrological drought of Karst drainage basins is shown the gradual aggravation from the west to east parts in South China, with the significant north–south stripe distributions at the SRI_3 and SRI_6; (ii) the occurring probability of hydrological droughts is the Limestone-type Karst Basin (II and III, 0.17) < Dolomite-type Karst Basin (I and IV, 0.22) < Non-Karst Basin (V, 0.25) in terms of combination types of basin lithologies, and (iii) the Karst Basin (I and III, 0.18) < Semi-Karst Basin (II and IV, 0.2) < Non-Karst Basin (V, 0.25) in terms of basin lithologies. Therefore, this proves that the most water-stored spaces are found in Karst Basins under the differential dissolution or erosion effects of soluble water, followed by in the Semi-Karst Basin, the least water-stored spaces in the Non-Karst Basin.

The Role of Large Dams in a Transboundary Drought Management Co-Operation Framework—Case Study of the Kabul River Basin

Hydrologic drought is a frequent phenomenon in the transboundary Kabul River Basin (KRB), the vital resource shared between the two nations of Afghanistan and Pakistan. While the KRB has vast water resources, these resources are subject to extreme hydrologic events and, as a result, are not adequately managed to deal with the stress during drought conditions in the transboundary setting with no formal agreement or treaty. Rapid population growth and increases in agricultural land will require balanced water distribution to meet the array of needs. The Soil and Water Assessment Tool (SWAT) is used to evaluate distribution options for flow frequencies under existing and proposed large dams in the headwaters of the KRB. The calibrated SWAT streamflow results are employed for statistical analyses of the Standardized Streamflow Index (SSI) and Annual Cumulative Deficit Volume (ACDV) to investigate hydrologic drought time series and identify the role of proposed dams to be used for drought mitigation. Based on the SSI, proposed dams can provide additional storage that will partially address hydrologic droughts in the future. At the same time, restrictions on agricultural land expansion and water intakes are other measures to facilitate balanced water resource availability. This study discusses the intricacies of transboundary conflict and cooperation, water rights, and drought risk management; as well, recommendations for a KRB transboundary Drought Task Force (DTF) between Afghanistan and Pakistan are provided, to develop a science-based policy for using the stored waters in large dams for drought relief, fairly and transparency.

Study On the Driven Mechanism of Watershed Hydrological Drought Based on Geomorphological Spatial Distribution Pattern: A Case Study of Guizhou, China

In recent years, hydrological drought has become more and more frequent, which has caused serious ecological and environmental problems. This paper is taking Guizhou province of China as an example to analyze the geomorphologic distribution and temporal-spatial evolution of hydrological droughts, and to study driving mechanisms of both the rainfall in the dry periods and geomorphologic factor on the hydrological droughts, based on the hydrometeorological data during the years 2000-2010, and the TM and DEM data. The results show that (1) the rainfall and its variation in the low-flow seasons have less impacts on the hydrologic drought and its variation; (2) the hydrologic drought severity in Guizhou was increasing year by year during the years 2000-2010, and showing the inter-annual variation with obvious stage characteristics, and the regional hydrologic drought was presented the more serious in the South than in the North, and the less serious in the East than in the West; and (3) in terms of the overall distribution of landform types, the mountain, hill and basin have less impacts on hydrological droughts; in terms of the distribution of single geomorphic type, hydrological droughts are significantly influenced by the high-medium mountain, deep-high hill and high basin, where the hydrological droughts are relatively lighter. While there are more serious areas in the low basin, shallow-low hill and low mountain.

Probabilistic Studies of Hydrologic Drought Events in Juba River in Somalia

Juba River runs from its headwaters in Ethiopia through Somalia and discharges into the Indian Ocean near Kismayo. Severe droughts recur in Juba River Catchment. This chapter examines the time series of hydrologic droughts and the factors influencing their occurrence in the catchment. The author further demonstrates the application of probability distributions to compute the exceedance probabilities of the hydrologic drought experienced in the catchment in the past, from 2001 to 2014. The fits of the probability distributions are compared to show the best fitting of all distributions. The probability distribution that will reasonably fit well to the data set is adapted to generate graphical plots for forecasting the return periods of drought events in the catchment. Reconstructing past drought episodes and future drought predictions is useful in drought risk management in Baardheere region of Somalia.