This document summarizes a study on reducing evaporation from dams in arid areas of northern Algeria. Evaporation rates were measured from four dams from 2000 to 2012 and found to be highly influenced by temperature and humidity, with significant evaporation occurring in summer months. The study tested using mixtures of hexadecanol and octadecanol on the water surface, which reduced evaporation by 30%. This technique was tested in the arid Hassi Ben Abdellah area, where temperatures exceed 91°F and humidity is low. The author recommends applying this technique to reduce evaporation, especially at Djorf-Torba dam that supplies water to agriculture and has a high evaporation volume.

1. Fifth International Conference on Climate Change Adaptation 2016
15-16 October 2016, Toronto, Canada
” Challenges & Issues in adaptation”
EVALUATION OF THE EVAPORATION RATE OF DAM LAKES IN ARID AREA
–NORTHERN ALGERIA-
Assia MEZIANI
PhD Student, University of Ouargla, department of Civil Engineering and Hydraulics, Ouargla, Algeria.
III.RESULTSII.MATERIAL AND METHOD
I.INTRODUCTION IV. CONCLUSIONS
FUTURE DIRECTIONS...
ACKNOWLEDGEMENTS
The climate data analysis of areas where the four dams are located,
have shown that these areas are characterized by a hyper- arid and an
arid climate. The Annual aridity index of Martonne varied from 3,20
to 9,89. From June to September, the precipitation was nearly zero
and the temperature reached a high value in this period. We notice a
large precipitation deficit developed in Djorf-Torba dam. The
evaporations from the fours dam lakes are related of temperature and
humidity. Significant evaporated water volumes were registered in
period of summer especially in Djorf-Torba and Brezina dam. To
reduce evaporation from water surface in these lakes or reservoirs,
we recommended using mixed films of hexadecanol and octadecanol
which showed efficacy to raise evaporation reduction to 30%.
Algeria is mainly an arid country, rainfall is particularly important. In fact, it
defines largely the bioclimatic zones of Algeria. The bioclimatic classification
of L. Emberger is based on climate characteristics affecting the plant cover
such as temperature, rainfall, evaporation, etc. The arid zones in Algeria covers
an area of 11,232,270 ha which have a much sparser vegetation cover, giving
meagre grazing on skeletal soils; they are at an advanced stage of degradation
(Nedjraoui, 2006). The rainfall deficit observed in recent decades is one of the
main causes of the desertification (Benslimane, 2008). The rainfall is less than
5,90 inches; the temperature is usually above 50 degrees Fahrenheit and the
evaporation ranges from 70 to 150 inch/year.
Figure 1. Map synthetic of sensitivity to desertification
(Benslimane, 2008).
An adequate technique experiment in arid area to reduce evaporation from water surface. The
objective of this technique is to conserve maximum water surface using chemical substances
(Hexadecanol (C16H34O) and Octadeanol (C18H38O)) capable of forming thin layers on the
water surface (called monomolecular films).
In Algeria, This technique is experimented during summer in arid area called Hassi Ben Abdellah
situated 27 Km in the northeast of Ouargla which temperature reached over 91,4°F with the
lowest relative humidity 19% and the wind speed varied from 10 to 30km/h. The value of rate of
the evaporation reduction is raised 30% where the monomolecular film is mixed of Hexadecanol
and Octadecanol (Seggai, 2012). According to the results obtained in laboratory conditions
showed that Hexadecanol did not have influence on the physico-chemical parameters, except
dissolved oxygen (Seggai, 2014)and the rates of the evaporation reduction depend on quantity of
Hexadecanol (concentration) used and on meteorological factors of the region (Seggai, 2014).
According to Berger(1953), the Hexadecanol did not create problems for water and the
octadecanol showed improved evaporation resistance and it has low toxicity.
We strongly suggest this technique specially to reduce evaporation from dams located in hyper-
arid area. In our case, the Djorf-Torba reservoir has a very high evaporated volume. We note that
the water of this dam is used for water supply of agricultural perimeters and drinking water
supply in the region (15 hm3 / year).
The objective of this paper is to analyze the rainfall, temperature, absolute humidity and
evaporation for twelve years of measurements. One of the best ways to measure evaporation from
lakes dams is using Colorado pan or class « A » pan they are frequently used to estimate the
evaporation. Each dam is equipped with a Colorado pan or class “A” pan installed restraint of
reservoir and buried in the ground. The measurement period starts from 2000 to 2012. The
evaporation and rainfall data have been obtained from ANBT (Agence Nationale des Barrages et
Transfers) and the temperature data have been collected from (www.infotclimat.fr) and the
absolute humidity have been calculated.
To clarify the type of climate in Biskra region, we calculated the monthly index of aridity; it was
calculated by Martonne formula which is:
I =12 P /(T+10)
P: Average monthly precipitation (mm)
T: Average monthly temperature (°C)
I: Monthly aridity index
First and foremost I offer my sincerest gratitude to Pr. Remini, who has
supported me to work in my own way. I have to express out appreciation
to Ossama Belafrag for sharing his knowledge with me during the course
of this research.
Fifth International Conference on Climate Change Adaptation 2016
15-16 October 2016, Toronto, Canada
” Challenges & Issues in adaptation”
EVALUATION OF THE EVAPORATION RATE OF DAM LAKES IN ARID AREA
–NORTHERN ALGERIA-
Assia MEZIANI
PhD Student, University of Ouargla, department of Civil Engineering and Hydraulics, Ouargla, Algeria.