Estimation of root zone salinity, using SaltMod, in the arid region of Turkey

Abstract

Soil salinity and waterlogging are the two most common problems limiting crop production in irrigated agriculture in southeastern Turkey. Poor water management and irrigation water leakage from the irrigation canals have caused the groundwater table to rise over approximately 35 000 ha of land. There is a need to predict drainage for salinity control in the Harran plain that has been under irrigation since 1995. The objective of this study was to establish the effects of current irrigation/drainage practices on root zone salinity, using SaltMod. Several scenarios like the changes in irrigation depth, water quality, varying drain spacing and drain depth effects on root zone salinity and groundwater table depth were tested. Experimental values showed that the initial average root zone salinity was 9.03 dS m RÉ SUMÉLa salinité du sol et l'engorgement sont les deux principaux problèmes qui limitent la production végétale dans l'agriculture irriguée dans le sud-est de la Turquie. Une gestion non satisfaisante de l'eau et les fuites des canaux d'irrigation ont fait s'élever la nappe sur approximativement 35 000 ha. Il est nécessaire de prévoir le drainage pour le contrôle de salinité dans la plaine de Harran qui est irriguée depuis 1995. L'objectif de cette étude était d'établir les effets des pratiques courantes d'irrigation/drainage sur la salinité de la zone racinaire à l'aide de SaltMod. Plusieurs scénarios, combinant profondeur d'irrigation, qualité de l'eau, espacement des drains et profondeur d'enfouissement des drains sur la zone des racines et sur la hauteur de la nappe, ont été étudiés. Les résultats montrent que la salinité moyenne initiale de la zone racinaire (9.03 dS m À1 ) a diminué après trois ans de saison d'irrigation (3.03 dS m À1 ). Ces valeurs sont très proches de celles calculées par le modèle SaltMod. Les débits de drainage mesurés pendant les trois années d'essai ont été de 0.099, 0.067 et 0.084 m/saison. SaltMod a montré que quand la profondeur d'enfouissement des drains atteint 1.40 m il n'y a aucun changement dans la salinité de la zone racinaire pendant les dix années qui suivent. Estimation de la salinité de la zone racinaire à l'aide de SaltMod dans la partie aride de la Turquie.

Field-evaluation of DRAINMOD-S for predicting soil and drainage water salinity under semi-arid conditions in Turkey

“…Currently, some computer simulation models can simulate surface and subsurface flows as well as chemical transport through soil [ANSWERS (Bouraoui et al, 2002), CREAMS (Knisel, 1980), GLEAMS (Knisel, 1993), SALTMOD (Bahceci et al, 2006;Bahçeci and Nacar, 2007), SWAT (Arnold et al, 1998), ADAPT (Alexander, 1988), andDRAINMOD (Skaggs, 1980)]. One of the most widely used models is DRAINMOD, developed by Skaggs (1976Skaggs ( , 1978.…”

Subsurface drainage and salt leaching in irrigated land in south‐east Turkey

“…Bahçeci and Nacar (2007) indicated with a model study that in the presence of a drainage system and when irrigation salinity content is 0.47 dS m À1 , root zone salinity will be reduced from 9.0 to 2.2 and 2.0 dS m À1 for the summer and winter seasons within 10 years of installing the drainage systems in the Harran plain.…”

“…In arid regions, subsurface drainage should be designed for long-term salinity control in the crop root zone, assuming good irrigation practices, while reducing mobilisation of salt below the root zone (Christen and Skehan, 2001). Bahçeci and Nacar (2007) indicated with a model study that in the presence of a drainage system and when irrigation salinity content is 0.47 dS m À1 , root zone salinity will be reduced from 9.0 to 2.2 and 2.0 dS m À1 for the summer and winter seasons within 10 years of installing the drainage systems in the Harran plain.…”

Performance assessment of subsurface drainage systems in the Harran Plain of the South‐East Anatolian region of Turkey

“…According to Bahçeci et al (2006), the SaltMod simulation results indicated that the drain depth could have been reduced to 1.20 m without harming agricultural production in the Konya–Cumra Plain. Simulated soil salinity results showed that most crops theoretically have no yield reduction when the depth of the water table is at 1.0 m. Bahçeci and Nacar (2007) pointed out that root zone salinity does not change for 10 years in the Harran Plain when the drainage depth is 1.0 m or deeper. On the other hand, SaltMod simulation results revealed that root zone salinity is expected to increase slightly when the drainage depth is reduced from 1.4 m to 1.2 m. However, considering the crop pattern in the plain, a significant yield reduction may not be expected.…”