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Journal of Environmental Hydrology
ISSN 1058-3912 |
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Electronic Journal of the International Association for
Environmental Hydrology
JEH Volume 15 (2007), Paper 29 Posted December 18, 2007 RELATIONSHIPS BETWEEN HYDROLOGICAL PARAMETERS USING CORRELATION AND TREND ANALYSIS, CRETE ISLAND, GREECE
T. Mavrommatis ABSTRACT The objective of this paper is to investigate the temporal relationship between the parameters of hydrologic balance in several basins on the island of Crete using correlation and trend analysis. Monthly rainfall totals, river discharge and estimated actual evapotranspiration (ET) from several representative basins in Crete were used. A moderate to strong association between the variations of rainfall and discharge was identified (r varied from 0.51 to 0.90). As a result, a greater than 66% rate of concurrent drought conditions for each river and its proximate rain gauge was found. In dry hydrological years river runoff decreased by 31% to 84%, compared to its mean annual rate. The change-point analysis detected increasing shifts in the second half of the 1980s in the mean of six out of nine annual time series of the ratio of precipitation to discharge. A second change, a diminishing in the rate, is estimated to have occurred around 1977/78. Only one site presented an increasing shift in the year-to-year variability, which occurred around 1984/85. A moderate association between the variations of rainfall and ET (r=0.63) resulted in greater than 50% of concurrent cases of meteorological and hydrological drought in three meteorological stations. At one out of three locations increases in the mean and standard deviation of the annual time series of the ratio of precipitation to ET were detected around 1998/99 and 1969/70 respectively, The time lag between the variations of rainfall with river flow variations ranged from 0 to 1. Zero to one month time lag was estimated from the cross-correlation analysis between rainfall totals and river discharges, while no time lag was observed between the former variable and ET. Reference: Mavrommatis, T., and K. Voudouris. 2007. Relationships between hydrological parameters using correlation and trend analysis, Crete Island, Greece. Journal of Environmental Hydrology, Vol. 15, Paper 29. CONTACT: Kostas Voudouris Lab. of Hydrogeology Dept. of Geology Aristotle University 54124, Thessaloniki Greece E-mail: kvoudour@geo.auth.gr |
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