CALCULATION OF DISTANCE BETWEEN DRAINS IN CONTROLLED REGIME PUBLISHEDRares Halbac-Cotoara-Zamfir, Ioana Alina Costescu
Controlled drainage is a method used for the integration of irrigation management with drainage management. It implies the reduction of drainage flow in order to maximize the crop’s water utilization. In the same time, controlled drainage prevents the humidity excess and the salts accumulation in soil profile. Controlled drainage has the potential to improve the efficiency of water utilization by maintaining high agricultural productions even in water scarcity situations and to assure the exploitation of land drainage systems with high benefits for farmers. Even the method has a large tradition in countries with experience in drainage field (USA, Netherlands), at this hour, in Romania, we don’t apply this type of drainage, the researches in this domain being at an incipient level. The formula recommended for the calculation of distance between drains, in controlled drainage regime, is a variation of Hooghoudt formula for drainage design, in a modified form initially proposed by Fox in 1956 and corrected to actual form by Ernst in 1975. This method uses Dupuit-Forchheimer assumptions of horizontal flow, Skaggs demonstrating that it is adequate for flow modelling in the case of subirrigation. In USA the researchers are using American standard EP 479 and subsequently modelling software specialized on drainage issues instead of selecting depths and distances between drains in the situation of designing a controlled drainage system. There are three possible types of errors which can appear in the situation of using the formula proposed by Hooghoudt. This errors are generated due to the difficulty of measuring very accurate the hydraulic conductivity and also due to different suppositions in installing a subirrigation system. This paper will present the results obtained in computing the distances between drains in controlled regime for soils with humidity excess from western Romania, being in this way an original paper. This paper is important because proposes a method which can proved to be very suitable for Timis County areas affected by humidity excess. In Timis County, during the last years, humidity excess alternated with drought periods. Taking in consideration this situation and the fact that only a relative small area is covered by irrigation arrangements (in comparison with the high area covered by drainage systems and the areas affected by water scarcity phenomenon) we can understand that controlled drainage can be a suitable solution as an efficient method to struggle drought effects by assuring an optimal level of soil humidity.
controlled drainage; efficiency; water utilization; drainage system