Analiza drenažnih kriterijuma kao uslov melioracija višeslojnih zemljišta aridnih regiona

Abstract

This study gives a detailed analysis of parameters for determination of basic criteria for field-pipe drainage, since desalinisation (Land Reclamation) and amelioration of degraded saline soils and its control require the existence of adequate ground drainage. For the purposes of drainage, pedological study was conducted and hydraulic conductivity measured in the selected horizons. Field measurements used standard augerhole method in saturated soil extract, below ground water level, for various depths to 5 m. For layers above ground water level and below it (if it was below drill depth), K- values were calculated based on: soil texture, average conductivity, via infiltration test, average filtration coefficient (100 ccm Kopecki), inverse augerhole method, while K- values for horizons of 0-2.5 and 2.5-3.5 were calculated based on the concept of transmissibility. The map of hydraulic conductivity was produced as the final result of the study, based on measured and estimated-calculated values. K-values (m/day) were classified into percentage categories (from 0.5 to > 4.0 m/day). Since soil desalinisation has three phases (initial leaching, reclamation-transitional production of tolerant crops, and regular crop production), it is clear that the drainage systems are projected for the third phase, therefore drainage quantities are defined as those that need to go through the drainage system in a given time in a given period, in order to maintain the rhizosphere salinity at the desired level. Drainage water quantity is the same as added water quantity (leaching requirements) in order to maintain the desired salinity level (4 mmhos/cm), with 25-30% of the gross irrigation requirements. Based on the gross irrigation and drainage requirements, the drainage hydromodule was determined at q = 2 mm/day. Important factors for subsurface-pipe drainage are depth and oscillations of ground water level in the growing period, or the minimum depth, which determines the aeration value and development of plant rhizosphere. The analysis verified that the drainage system designed for permanent requirements in the regular production phase can satisfy temporary drainage requirements at the initial leaching phase. Finally, field drainage depth must be higher than minimum depth of ground water, so that hydraulic head is provided which causes movement of ground water towards the drain. Adopted field drain depth is 2.0-2.5 m. As the final result of the applied methods, and based on hydro-pedological soil properties and their analyses, the modified Hooghoudt-Ernst equation was used to calculate field drain spacing. By using the aforementioned calculation method, the drainage spacing is adopted as follows: 45 m, 60 m, 75 m, 90 m, 105 m, and 120 m, while average drainage depth is 2.3 m.