JEB logo

Journal of Environmental Biology

pISSN: 0254-8704 ; eISSN: 2394-0379 ; CODEN: JEBIDP

About Journal
    Editor in Chief
    Editorial Board
    Reviewer Panel
    Publication Policies
    Guidelines for Editors
    Guidelines for Reviewers
    Abstracting and Indexing
    Subscription and Payments
    Contact Journal
Read Journal
    Current Issue
    Journal Archives
For Authors
    Guidelines for Authors
    Terms and Conditions
    Fees and Payments
    Track Paper Status
    JEB Awards

Google Search the Journal web-site:

    Abstract - Issue Apr Supplement 2012, 33 (2)                                     Back

nstantaneous and historical temperature effects on a-pinene

Analysis of the climate variability on Lake Nasser evaporation

based on the Bowen ratio energy budget method


Author Details


Mohamed Elsawwaf (Corresponding author)

Hydraulics Laboratory, Department of Civil Engineering, Katholieke Universiteit Leuven, Kasteelpark

Arenberg 40, 3001 Heverlee

Water Resources Research Institute, National Water Research Center, El-Qanater El-Khiria. 13621,



Patrick Willems

Hydraulics Laboratory, Department of Civil Engineering, Katholieke Universiteit Leuven, Kasteelpark

Arenberg 40, 3001 Heverlee, Belgium


Publication Data

Paper received:

25 October 2010


Revised received:

05 July 2011



30 July 2011



Variations in lake evaporation have a significant impact on the energy and water budgets of lakes. Understanding these variations and the role of climate is important for water resources management as well as predicting future changes in lake hydrology as a result of climate change. This study presents a comprehensive, 10-year analysis of seasonal, intraseasonal, and interannual variations in lake evaporation for Lake Nasser in South Egypt. Meteorological and lake temperature measurements were collected from an instrumented platform (Raft floating weather station) at 2 km upstream of the Aswan High Dam. In addition to that, radiation measurements at three locations on the lake: Allaqi, Abusembel and Arqeen (respectively at 75, 280 and 350 km upstream of the Aswan High Dam) are used. The data were analyzed over 14-day periods from 1995 to 2004 to provide bi-weekly energy budget estimates of evaporation rate. The mean evaporation rate for lake Nasser over the study period was 5.88 mm day-1, with a coefficient of variation of 63%. Considerable variability in evaporation rates was found on a wide range of timescales, with seasonal changes having the highest coefficient of variation (32%), followed by the intraseasonal (28%) and interannual timescales (11.6%; for summer means). Intraseasonal changes in evaporation were primarily associated with synoptic weather variations, with high evaporation events tending to occur during incursions of cold, dry air (due, in part, to the thermal lag between air and lake temperatures). Seasonal variations in evaporation were largely driven by temperature and net energy advection, but are out-of-phase with changes in wind speed. On interannual timescales, changes in summer evaporation rates were strongly associated with changes in net energy advection and showed only moderate connections to variations in temperature or humidity.


Key words

Lake Nasser, Energy budget, Climate variability, Bowen ratio energy budget (BREB)


Copyright © 2012 Triveni Enterprises. All rights reserved. No part of the Journal can be reproduced in any form without prior permission.¬†Responsibility regarding the authenticity of the data, and the acceptability of the conclusions enforced or derived, rest completely with the author(s).