Effect of Relative humidity on Volumetric water content over Selected stations in Iraq

Abstract

Volumetric water content (VWC) is the ratio of the volume of water to a unit volume of soil. It can be expressed as
a percentage or depth of water per soil depth, and it is one of the important factors in determining agricultural
drought-related development of water present in soil and water in land surfaces not found in rivers, lakes or
groundwater but rather than It resides in the pores of the soil, and relative humidity is the concentration of water
vapor present in the air. Water vapor is the gaseous state of water and is generally invisible to the human eye.
Humidity indicates the possibility of precipitation, dew or mist, the humidity depends on the temperature and
pressure of the system in question. The same amount of water vapor produces more moisture in cold air than it
does in warm air. The relevant variable is the degree of dew point. The amount of water vapor needed to achieve
saturation increases with increasing temperature. As the temperature of a specific portion of the air decreases, it
will eventually reach its saturation point without adding or losing mass of water.
The data was obtained from the European Center (ECMWF), which includes the average monthly and annual
relative humidity and water content of soil, for a period of 30 years from (1988-2018) for four selected stations
over Iraq. The lowest values of relative humidity were recorded in July and August. The highest value of relative
humidity was in the months of December and January accompanied by a decrease in temperature and dew. We note
from the results that there is a positive relationship between RH% and VSWC for soil. The highest value for the
water content was in Mosul and the lowest in Basra, the reason is due to meteorological factors, and the results
show that the strong correlation is in all study stations.