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Characteristics of Lake Chad level variability and links to ENSO, precipitation, and river discharge.

Okonkwo C, Demoz B, Gebremariam S - ScientificWorldJournal (2014)

Bottom Line: The wavelet transform coherency (WTC) between LC level of the southern pool at Kalom and ENSO is statistically significant at the 95% confidence level and phase-locked, implying a cause-and-effect association.These strong coherencies coincide with the La Niña years with the exception of 1997-1998 El Niño events.Implications for water resource planning and management are discussed.

View Article: PubMed Central - PubMed

Affiliation: Beltsville Center for Climate System Observation (BCCSO), Atmospheric Science Program, Howard University, Washington, DC 20059, USA.

ABSTRACT
This study used trend, correlation, and wavelet analysis to characterize Lake Chad (LC) level fluctuations, river discharge, El Niño Southern Oscillation (ENSO), and precipitation regimes and their interrelationships. Linear correlation results indicate a negative association between ENSO and LC level, river discharge and precipitation. Trend analysis shows increasing precipitation in the Lake Chad Basin (LCB) but decreasing LC level. The mode of interannual variability in LC level, rainfall, and ENSO analyzed using wavelet analysis is dominated by 3-4-year periods. Results show that variability in ENSO could explain only 31% and 13% of variations in LC level at Kindjeria and precipitation in the northern LCB, respectively. The wavelet transform coherency (WTC) between LC level of the southern pool at Kalom and ENSO is statistically significant at the 95% confidence level and phase-locked, implying a cause-and-effect association. These strong coherencies coincide with the La Niña years with the exception of 1997-1998 El Niño events. The WTC shows strong covariance between increasing precipitation and LC level in the northern pool at a 2- to 4-year band and 3- to 4-year band localized from 1996 to 2010. Implications for water resource planning and management are discussed.

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Schematics of the state of Lake Chad (modified from Landsat 5 images; courtesy of NASA).
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fig1: Schematics of the state of Lake Chad (modified from Landsat 5 images; courtesy of NASA).

Mentions: A summary of the historical changes in LC is given in Figure 1 with the classification of various states of the lake as proposed by Singh et al. [4, 28]. The figure shows the dramatic decrease in lake size from about 24,000 km2 in the 1950s (Large Lake Chad) to about 18,000 km2 in the early 1970s (Normal Lake Chad). Drought during the late 1960s and early 1970s led to the splitting of the single lake into northern (Sahara-arid) and southern (Savanna-humid) pools around 1975 [4]. Recently, [4] added a new category called a Dry Small Lake Chad with the northern pool permanently dry most of the year.


Characteristics of Lake Chad level variability and links to ENSO, precipitation, and river discharge.

Okonkwo C, Demoz B, Gebremariam S - ScientificWorldJournal (2014)

Schematics of the state of Lake Chad (modified from Landsat 5 images; courtesy of NASA).
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4265694&req=5

fig1: Schematics of the state of Lake Chad (modified from Landsat 5 images; courtesy of NASA).
Mentions: A summary of the historical changes in LC is given in Figure 1 with the classification of various states of the lake as proposed by Singh et al. [4, 28]. The figure shows the dramatic decrease in lake size from about 24,000 km2 in the 1950s (Large Lake Chad) to about 18,000 km2 in the early 1970s (Normal Lake Chad). Drought during the late 1960s and early 1970s led to the splitting of the single lake into northern (Sahara-arid) and southern (Savanna-humid) pools around 1975 [4]. Recently, [4] added a new category called a Dry Small Lake Chad with the northern pool permanently dry most of the year.

Bottom Line: The wavelet transform coherency (WTC) between LC level of the southern pool at Kalom and ENSO is statistically significant at the 95% confidence level and phase-locked, implying a cause-and-effect association.These strong coherencies coincide with the La Niña years with the exception of 1997-1998 El Niño events.Implications for water resource planning and management are discussed.

View Article: PubMed Central - PubMed

Affiliation: Beltsville Center for Climate System Observation (BCCSO), Atmospheric Science Program, Howard University, Washington, DC 20059, USA.

ABSTRACT
This study used trend, correlation, and wavelet analysis to characterize Lake Chad (LC) level fluctuations, river discharge, El Niño Southern Oscillation (ENSO), and precipitation regimes and their interrelationships. Linear correlation results indicate a negative association between ENSO and LC level, river discharge and precipitation. Trend analysis shows increasing precipitation in the Lake Chad Basin (LCB) but decreasing LC level. The mode of interannual variability in LC level, rainfall, and ENSO analyzed using wavelet analysis is dominated by 3-4-year periods. Results show that variability in ENSO could explain only 31% and 13% of variations in LC level at Kindjeria and precipitation in the northern LCB, respectively. The wavelet transform coherency (WTC) between LC level of the southern pool at Kalom and ENSO is statistically significant at the 95% confidence level and phase-locked, implying a cause-and-effect association. These strong coherencies coincide with the La Niña years with the exception of 1997-1998 El Niño events. The WTC shows strong covariance between increasing precipitation and LC level in the northern pool at a 2- to 4-year band and 3- to 4-year band localized from 1996 to 2010. Implications for water resource planning and management are discussed.

Show MeSH
Related in: MedlinePlus