Analysis of drought conditions and their effects on Lake Trasimeno (Central Italy) levels

An analysis of drought conditions on the Lake Trasimeno area (Umbria, Central Italy) and of their influence on the lake levels is presented. Lake Trasimeno is one of the largest Italian lakes, and its economic and environmental importance is very high. The analysis of temperature data (1963-2014) shows that annual temperature is increasing – in accordance with what is known for Central Italy and the Mediterranean area – with a significant gradient of about 0.023°C/ year. No significant annual and seasonal rainfall trends were observed over the Lake Trasimeno catchment. The power spectrum analysis of rainfall and lake level fluctuations shows that both periodograms have high statistical confidence levels (>99%) for annual and semi-annual cycles. The annual cycles of the periodogram of lake level fluctuations show a higher statistical confidence level than semi-annual cycles. Some other cycles such as the El-Niño Southern oscillation, North Atlantic oscillation, and solar activity are highlighted, with significance levels lower than that of annual and semi-annual cycles. The standardized precipitation (SPI) and standardized reconnaissance drought indices, at different time scales, show that frequency and duration of extreme and severe droughts have increased in the last 25 years. A significant relationship between 12-month SPI and 12-month standardized lake levels fluctuations was obtained for the 1989-2014 period, indicating that SPI12 can be a useful indicator to represent drought severity for systems such as the Lake Trasimeno by considering lake level fluctuations rather than lake levels.

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The use of multiple dendrochronological techniques to develop a 200-year drought record for subtropical Southeast Queensland, Australia

10.5194/egusphere-egu2020-11768 ◽

2020 ◽

Author(s):

Heather A Haines ◽

Jonathan G Palmer ◽

Nathan B English ◽

Quan Hua ◽

Patricia S Gadd ◽

...

Keyword(s):

Tree Ring ◽

Southern Oscillation ◽

Ring Width ◽

Drought Indices ◽

Drought Severity ◽

Age Validation ◽

Climate Reconstructions ◽

Drought Conditions ◽

Southeast Queensland

In Australia the majority of tropical and subtropical regions lack any long-term (multi-decadal to centennial scale) instrumental climate records highlighting a need for alternatives such as proxy climate reconstructions. Despite this need, only a limited number of terrestrial proxy sources are available. Tree-rings provide one of the few options for climate reconstructions yet very little dendrochronological investigation has been undertaken as early assessments of tropical Australian species in the 1970s and 1980s indicated most species had short life-spans, poorly preserved timbers, or were compromised by having many ring anomalies. There has also been limited effort into understanding the growth-climate relationships of these trees with only a few studies undertaken targeting specific species that have unfortunately been heavily cleared from the region (eg. Toona ciliata). One exception noted in the early species assessment suggested that trees in the Araucariaceae family, a common tree family along the tropical Australian east coast, is longer lived than many other species in the region, contains growth rings which are annual in nature, and grows in response to climatic conditions.Here we describe the results from a stand of Araucaria cunninghamii trees located in Lamington National Park, a World Heritage listed rainforest in subtropical Southeast Queensland, Australia (a region known for experiencing extreme hydroclimatic events). Our assessment discovered the presence of false, faint, locally absent, and pinching rings. By combining traditional dendrochronological analysis (eg. crossdating) with more recent techniques such as age validation by bomb-pulse radiocarbon dating and tree-ring density analysis, a robust ring-width chronology from 1805-2014 was developed. Dendrometers installed on four trees at the Lamington site confirmed that tree growth was annual and that moisture sensitivity was driving growth. Further growth-climate analysis indicated that the strongest correlation to the tree-ring chronology was specifically related to drought conditions in the region. The strength of this response was compared to both local and regional spatial areas and to drought indices such as the self-calibrating Palmer Drought Severity Index (scPDSI), the Standardized Precipitation Evaporation Index (SPEI), and the long-term drought conditions shown by the Australian and New Zealand Drought Atlas (ANZDA). The combined analysis led to the development of a 200-year drought reconstruction for the region and demonstrates influences from both the El Ni&#241;o Southern Oscillation (ENSO) and the Interdecadal Pacific Oscillation (IPO).

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Multivariate framework for the assessment of key forcing to Lake Malawi level variations in non-stationary frequency analysis

Environmental Monitoring and Assessment ◽

10.1007/s10661-020-08519-4 ◽

2020 ◽

Vol 192 (9) ◽

Author(s):

Cosmo Ngongondo ◽

Yanlai Zhou ◽

Chong-Yu Xu

Keyword(s):

Lake Level ◽

Southern Oscillation ◽

Low Frequency ◽

Lake Malawi ◽

Extreme Value ◽

Information Criteria ◽

Eastern Africa ◽

Water Evaporation ◽

Lake Levels ◽

Indian Ocean Dipole Mode

Abstract Lake Malawi in south eastern Africa is a very important freshwater system for the socio-economic development of the riparian countries and communities. The lake has however experienced considerable recession in the levels in recent years. Consequently, frequency analyses of the lake levels premised on time-invariance (or stationarity) in the parameters of the underlying probability distribution functions (pdfs) can no longer be assumed. In this study, the role of hydroclimate forcing factors (rainfall, lake evaporation, and inflowing discharge) and low frequency climate variability indicators (e.g., El Nino Southern Oscillation-ENSO and the Indian Ocean Dipole Mode-IODM) on lake level variations is investigated using a monthly mean lake level dataset from 1899 to 2017. Non-stationarity in the lake levels was tested and confirmed using the Mann-Kendall trend test (α = 0.05 level) for the first moment and the F test for the second moment (α = 0.05 level). Change points in the series were identified using the Mann-Whitney-Pettit test. The study also compared stationary and non-stationary lake level frequency during 1961 to 2004, the common period where data were available for all the forcing factors considered. Annual maximum series (AMS) and peak over threshold (POT) analysis were conducted by fitting various candidate extreme value distributions (EVD) and parameter fitting methods. The Akaike information criteria (AIC), Bayesian information criteria (BIC), deviance information criteria (DIC), and likelihood ratios (RL) served as model evaluation criteria. Under stationary conditions, the AMS when fitted to the generalized extreme value (GEV) distribution with maximum likelihood estimation (MLE) was found to be superior to POT analysis. For the non-stationary models, open water evaporation as a covariate of the lake levels with the GEV and MLE was found to have the most influence on the lake level variations as compared with rainfall, discharge, and the low frequency climatic forcing. The results are very critical in flood zoning especially with various planned infrastructural developments around the lakeshore.

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Global Maps of Lake-Level Fluctuations since 30,000 yr B.P.

Quaternary Research ◽

10.1016/0033-5894(79)90092-9 ◽

1979 ◽

Vol 12 (1) ◽

pp. 83-118 ◽

Cited By ~ 415

Author(s):

F. Alayne Street ◽

A. T. Grove

Keyword(s):

Lake Level ◽

Ice Sheets ◽

Literature Survey ◽

Sea Surface ◽

Lake Levels ◽

Lake Level Fluctuations ◽

Average Abundance ◽

The Tropics ◽

High Lake Levels ◽

Precipitation And Temperature

This paper presents selected world maps of lake-level fluctuations since 30,000 yr B.P. These are based on a literature survey of 141 lake basins with radiocarbon-dated chronologies. The resulting patterns are subcontinental in scale and show orderly variations in space and time. They reflect substantial changes in continental precipitation, evaporation, and runoff, which are due to glacial/interglacial fluctuations in the atmospheric and oceanic circulations. In the tropics, high lake levels are essentially an interglacial or interstadial phenomenon, although there are important exceptions. Since extensive lakes during the Holocene corresponded with relatively high sea-surface temperatures, and therefore presumably with high evaporation rates on land, they are interpreted as the result of higher precipitation. Tropical aridity culminated in most areas at, or just after, the glacial maximum, although the present day is also characterized by a below-average abundance of surface water. In extratropical regions the mapped patterns are more complex. They vary markedly with latitude and proximity to major ice sheets. In these areas, evidence is at present insufficient to evaluate the relative contributions of precipitation and temperature to the observed lake-level record.

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Evaluation of the similarity between drought indices by correlation analysis and Cohen's Kappa test in a Mediterranean area

Natural Hazards ◽

10.1007/s11069-021-04775-w ◽

2021 ◽

Author(s):

L. Vergni ◽

F. Todisco ◽

B. Di Lena

Keyword(s):

Correlation Analysis ◽

Pearson Correlation ◽

Central Italy ◽

Meteorological Drought ◽

Drought Indices ◽

Drought Severity ◽

Cohen’S Kappa ◽

Kappa Test ◽

Cohen's Kappa ◽

Standardised Precipitation Index

AbstractIn the literature, numerous papers report comparative analyses of drought indices. In these types of studies, the similarity between drought indices is usually evaluated using the Pearson correlation coefficient, r, calculated between corresponding severity time series. However, it is well known that the correlation does not describe the strength of agreement between two variables. Two drought indices can exhibit a high degree of correlation but can, at the same time, disagree substantially, for example, if one index is consistently higher than the other. From an operational point of view, two indices can be considered in agreement when they indicate the same severity category for a given period (e.g. moderate drought). In this work, we compared six meteorological drought indices based on both correlation analysis and Cohen's Kappa test. This test is typically used in medical or social sciences to obtain a quantitative assessment of the degree of agreement between different methods or analysts. The indices considered are five timescale-dependent indices, i.e. the Percent of Normal Index, the Deciles Index, the Percentile Index, the Rainfall Anomaly Index, and the Standardised Precipitation Index, computed at the 1-, 3-, and 6-month timescales, and the Effective Drought Index, a relatively new index, which has a self-defined timescale. The indices were calculated for 15 stations in the Abruzzo region (central Italy) during 1951–2018. We found that the strength of agreement depends on both the criteria of drought severity classification and the different indices' calculation method. The Cohen's Kappa test indicates a prevailing moderate or fair agreement among the indices considered, despite the generally very high correlation between the corresponding severity times series. The results demonstrate that the Cohen's Kappa test is more effective than the correlation analysis in discriminating the actual strength of agreement/disagreement between drought indices.

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Comparative evaluation of precipitation-temperature based drought indices (DIs): A case study of Moroccan Lower Sebou basin

Kuwait Journal of Science ◽

10.48129/kjs.13911 ◽

2021 ◽

Author(s):

Oualid HAKAM ◽

◽

Abdennasser BAALI ◽

Touria EL KAMEL ◽

Ahouach Youssra ◽

...

Keyword(s):

Drought Index ◽

River Flow ◽

Potential Evapotranspiration ◽

Standardized Precipitation Index ◽

Data Availability ◽

Drought Indices ◽

Drought Severity ◽

Drought Event ◽

Precipitation Temperature ◽

Drought Conditions

Due to the lack of studies on drought in the Lower Sebou basin (LSB), the complexity of drought event and the difference in climate conditions. The identification of the most appropriate drought indices (DIs) to assess drought conditions has become a priority. Therefore, assessing the performance of different drought indices was considered in order to identify the universal drought indices that are well adapted to the LSB. Based on data availability, five DIs were used: Standardized Precipitation Index (SPI), Standardized Precipitation and Evapotranspiration Index (SPEI), Reconnaissance Drought Index (RDI), self-calibrated Palmer Drought Severity Index (sc-PDSI) and Streamflow Drought Index (SDI). The DIs were calculated on an annual scale using monthly time series of precipitation, temperature and river flow from 1984-2016. Thornthwaite's method was used to calculate potential evapotranspiration (PET). Pearson's correlation (r) were analyzed. Furthermore, five decision criteria namely robustness, traceability, transparency, sophistication and scalability were used to evaluate the performance of these indices. The results proved the fact that SPI is suitable to detect the drought duration and intensity compared to other indices with high correlation coefficients especially in sub humid regions, knowing that it tends to give more results that are humid in stations with semi-arid climates. SPI, SPEI and RDI follow the same trend during the period studied. However, sc-PDSI appears to be the most sensitive to temperature and precipitation by overestimating the drought conditions. Eventually, the results of the performance evaluation criteria revealed that SPEI classified first (total score = 137) among other meteorological drought indices, followed by SPI, RDI and sc-PDSI.

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Drought Monitoring Using Rainfall, Evapotranspiration and Streamflow Data: A Case Study of Kaduna River Catchment Area (Nigeria)

Journal of Scientific Research and Reports ◽

10.9734/jsrr/2020/v26i830303 ◽

2020 ◽

pp. 133-144

Author(s):

A. Dare ◽

E. J. Zakka ◽

Maikano Samson ◽

A. O. Afolabi ◽

S. O. Okechalu ◽

...

Keyword(s):

Catchment Area ◽

Drought Index ◽

Meteorological Data ◽

Standardized Precipitation Index ◽

Hydrological Drought ◽

Crop Damage ◽

Drought Monitoring ◽

Drought Indices ◽

Drought Severity ◽

Drought Conditions

Drought is defined as the lack of adequate precipitation, either rain or snow that causes reduced soil moisture or groundwater, diminished streamflow, crop damage and a general water shortage. The objective of this study focuses on meteorological and hydrological drought monitoring in river Kaduna catchment area. Standardized Precipitation Index (SPI) and Reconnaissance Drought Index (RDI) drought indices were used to characterize meteorological drought while Streamflow Drought Index (SDI) was used for hydrological drought monitoring for a period of 34 years (1967 – 2001). DrinC software, a drought indices calculator, was used for the calculation of SPI, RDI, and SDI respectively. The drought severity classification based on meteorological and hydrological drought indices gave 33% and 37% drought conditions period with the year 1967 – 2001. Based on these indexes, the drought characteristics of the catchment area were investigated by analyzing meteorological data from 1967 to 2001. The results of this analysis show that more non-drought/normal conditions were predominant than drought conditions. During the period under study (34 years), only one-year return period of extreme drought condition.

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Late Pleistocene highstand and recession of a small, high-altitude pluvial lake, Jakes Valley, central Great Basin, USA

Quaternary Research ◽

10.1016/j.yqres.2005.08.025 ◽

2006 ◽

Vol 65 (1) ◽

pp. 179-186 ◽

Cited By ~ 22

Author(s):

Antonio Francisco García ◽

Martin Stokes

Keyword(s):

High Altitude ◽

Great Basin ◽

Late Pleistocene ◽

Lake Level ◽

Storm Track ◽

Jet Stream ◽

Lake Levels ◽

Lake Level Fluctuations

AbstractModels of factors controlling late Pleistocene pluvial lake-level fluctuations in the Great Basin are evaluated by dating lake levels in Jakes Valley. “Jakes Lake” rose to a highstand at 13,870 ± 50 14C Yr B.P., receded to a stillstand at 12,440 ± 50 14C yr B.P., and receded steadily to desiccation thereafter. The Jakes Lake highstand is roughly coincident with highstands of lakes Bonneville, Lahontan and Russell. The rise to highstand and recession of Jakes Lake were most likely controlled by a storm track steered by the polar jet stream. The final stillstand of Jakes Lake helps constrain timing of northward retreat of the polar jet stream during the Pleistocene–Holocene transition.

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Interannual Hydroclimatic Variability of the Lake Mweru Basin, Zambia

Water ◽

10.3390/w11091801 ◽

2019 ◽

Vol 11 (9) ◽

pp. 1801 ◽

Cited By ~ 2

Author(s):

Peter Waylen ◽

Christopher Annear ◽

Erin Bunting

Keyword(s):

Interannual Variability ◽

Lake Level ◽

Southern Oscillation ◽

Breeding Habitat ◽

Fish Populations ◽

Annual Precipitation ◽

Data Sets ◽

Lake Levels ◽

Wetland Complex ◽

Hydroclimatic Variability

Annual precipitation inputs to the Lake Mweru basin, Zambia, were computed from historic data and recent gridded data sets to determine historic (1925–2013) changes in lake level and their potential impacts on the important fisheries of the lake. The results highlight a period from the early 1940s to the mid-1960s when interannual variability of inputs doubled. Existing lake level data did not capture this period but they did indicate that levels were positively correlated with precipitation one to three years previously, reflecting the hydrologic storage of the lake, the inflowing Luapula River and the upstream Bangweulu wetland complex. Lag cross-correlations of rainfall to El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole were weak and spatially and temporally discontinuous. The two drivers were generally positively correlated and induced opposing effects upon annual precipitation and lagged lake levels. This correlation became non-significant during the time of high observed interannual variability and basin inputs were prone to the vagaries of either driver independently or reinforcing drought/excess conditions. During times of high flows and persistent elevated lake levels, breeding habitat for fish increased markedly, as did nutrition supplied from the upstream wetlands. High hydrologic storage ensures that lake levels change slowly, despite contemporary precipitation totals. Therefore, good conditions for the growth of fish populations persisted for several years and populations boomed. Statistical models of biological populations indicated that such temporally autocorrelated conditions, combined with abundant habitat and nutrition can lead the “boom and bust” of fish populations witnessed historically in Lake Mweru.

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A Decade of Hydrological Drought in Central-Western Argentina

Frontiers in Water ◽

10.3389/frwa.2021.640544 ◽

2021 ◽

Vol 3 ◽

Author(s):

Juan A. Rivera ◽

Sebastián Otta ◽

Carolina Lauro ◽

Natalia Zazulie

Keyword(s):

Groundwater Resources ◽

Snow Accumulation ◽

Hydrological Drought ◽

Mitigation Strategies ◽

Drought Indices ◽

Drought Severity ◽

Equivalent Thickness ◽

Wine Production ◽

Drought Conditions ◽

Central Western Argentina

Most of the water used for the development of the main socio-economic activities in Central-Western Argentina (CWA), an arid to semi-arid region, home to most of the Argentinean wine production, relies on surface streamflow from several snow-fed rivers. During the last decade (2010-2020), reduced snow accumulation over the higher elevations of the Andes mountains triggered the occurrence of hydrological drought over CWA, affecting winter tourism, restricting water use for irrigation and domestic use, and leading to socio-political disputes. This study provides a detailed description of the recent hydrological drought conditions through the use of streamflow records from 15 river basins, which were complemented by precipitation, snowpack, and water equivalent thickness measurements to provide a comprehensive picture of the water losses over the last decade. Hydrological drought indices derived from the threshold level method and the standardized streamflow index allowed characterizing the unusualness of this dry period in the context of the last 49 years. The hydrological deficit over the last decade highlighted the challenges faced by the water managers to provide water for irrigation in the main agricultural oases, with a likely overexploitation of the groundwater resources to supplement the limited surface runoff. The hydrological drought severity increased since 2017, with record-breaking levels in several basins, particularly during the period between July 2019 and June 2020 for the rivers located between 35° and 36°S. We identified the main hydrological drought impacts in CWA, as well as the need for improved mitigation strategies to cope with current and future drought conditions. We also analyzed the current limitations in terms of snow and groundwater observations, highlighting the necessity for an effective hydrological drought monitoring system, together with an improved forecast of snow accumulation in the headwaters, which can contribute to better regional water management plans.

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Practical tool for drought characteristics calculation

10.5194/egusphere-egu21-14328 ◽

2021 ◽

Author(s):

Mahyar Mottaghi Zadeh ◽

Maral Habibi

Keyword(s):

Quantitative Description ◽

Geographical Location ◽

Drought Indices ◽

Drought Severity ◽

Drought Condition ◽

Development Environment ◽

Drought Duration ◽

Software Application ◽

Drought Characteristics ◽

Drought Conditions

There are many ways to identify and monitor drought conditions. Scarcely are tools that calculate drought characteristics, The "SDF Calculator" works to bring monitoring tools to the public so they can assess drought conditions, this tool is used to assess and identify drought and its intensity.Drought severity refers to the absolute sum of consecutive SDI values below a given threshold level while drought duration is the number of consecutive months that SDI is below that threshold, and drought frequency is a number of months with drought condition (means SPI < -0.5 or any given threshold that is desire, the threshold of drought index is a value that an index faces to drought condition. In every index, this value can be changed. For example, in many indices, the threshold of drought starts from zero or less zero. In other words, when the value of an index is calculating then all the values located in the drought classes, refer to the severity of the drought.Droughts and exceptionally wet periods are regional phenomena, which are considered as major environmental extremes, especially in semiarid regions of the world. The development of severity-duration-frequency (SDF) relationships of droughts and wet periods is important in hydrological and climatic plannings in any country.In this study, we aimed to offer a novel software model to be used for a quantitative description of droughts and wet periods to provide an overview of drought intensity and analyzing their severity, frequency, and duration. In addition, we have been able to develop a state-of-the-art bespoke software application, so the users are able to analyze drought based on the regional thresholds. While most of the analysis applications have used programming languages such as R or Python, due to the lack of software libraries in the .NET development environment, we have managed to offer our development environment based on .NET Core and C# programming language. The software application accepts inputs from various file formats or APIs, processes the data, and demonstrates the outcome in different graphs and maps depending on the geographical location of study areas. The outputs are not only can be exported as different formats to be used in big data applications but also might be exposed as web APIs to be used in live applications.&#160;&#160;Keywords: Drought characteristics, SDF Calculator, API, Standardized Drought Indices (SDI)

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