Prediction of the hydraulic properties of the dominant soils in Erbil Governorate

Other Title(s)

تَقدير الصفات الهيدروليكية للترب السائدة في محافظة أربيل

Dissertant

Abd Allah, Azad Salih

Thesis advisor

Karim, Tariq Hama

Comitee Members

Dahham, Faysal A.
Hachum, Ahmad Y.
al-Hadithi, Jabir I. Khalaf

University

Salahaddin University-Hawler

Faculty

Agriculture College

University Country

Iraq

Degree

Master

Degree Date

2012

English Abstract

To formulate soil water relationships, soil hydraulic properties are required as essential inputs.

The most important hydraulic properties are the soil water retention curve SWRC and the hydraulic conductivity K (h).

Besides the need of the former for calculating plant available water, its parameterization is required to compute soil water fluxes in unsaturated soils.

However in Iraqi Kurdistan region soil water retention data is only sparsely available.

Therefore, this study was undertaken with the main objective of specifying the parameters of the water retention equations which offered the highest performance in describing the water retention characteristic of the most popular soils surrounding Erbil city.

Additionally, several trials have been made to correlate the determined parameters with other basic soil properties and the possibility of predicting K (h) from SWRC.

To achieve the above objectives, intact samples were obtained from the surface layer of Erbil plain and its surrounding.

Soil water retention curves were obtained by using the combination of hanging water column and pressure plate methods, while K (h) was measured by following the upward infiltration method.

The results indicated that the general shape of the SWRC is sigmoidal with three identifiable stages of desaturation.

The van Genuchten model scored best in describing the soil moisture characteristic curve followed by Williams et al, and Karim models.

Among the basic soil properties, macroporosity was high significantly correlated with most of the study parameters.

Additionally, strong interrelations were observed between the parameters of the study models.

Moreover, the results indicated that the degree of hysteresis varied linearly with the air entry value.

There was a reasonable agreement between the measured saturated hydraulic conductivity Ks and predicted values by following the Koorevaar et al.

procedure, but they were significantly different from those obtained by Marshall Method.

On the other hand the K (h) values obtained by Jackson’s method were underestimated and the differences exceed two orders of magnitude.

Further, the results pointed out that the closed form of BC model performed K (h) better than that of the VG model.

The water content retained at -1500 kPa exhibited the strongest correlation with soil water content retained at -33 kPa, followed by plasticity index, clay content and sand content.

Apart from this, it was noticed that the plasticity index exhibited the strongest correlation with soil water content retained at -1.5MPa followed by clay and sand contents.

The results also indicated that the agreement between SWRC measured by using tensiometer and combination of hanging water column and pressure plate methods was reasonable over the range of soil water content from 0 to about 200 cm H2O.

Additionally, a satisfactory agreement was observed between the values of K (h) obtained by upward infiltration and instantaneous profile methods for h.

Main Subjects

Earth Sciences, Water and Environment

Topics

• Iraq
• Irbil

No. of Pages

148

Table of Contents

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-314596