ABSTRACT
I. VARLEV Research Institute of Irrigation, Drainage and Hydraulic Engineering, Sofia, Bulgaria Z POPOVA Institute of Soil Science and Agroecology 'N. Pushkarov', Sofia, Bulgaria I. GOSPODINOV Experimental Station, Stara Zagora, Bulgaria
Abstract Surge irrigation is defined as on and off cycles of stream delivered at the head of the furrows. Usually on - and off - time are constant during surge irrigation event. Surge irrigation have been tested in Bulgaria for different furrow length (from 100 to 700 m), soil and terrain conditions since 1965. Water saving is studied separately over first and second phase of stream advance and registered surge effect is compared for the studied situations. During the first phase streams advance traditionally non - uniformly over the surface of a furrow set which usually includes more then 1 5 - 2 0 simultaneously irrigated furrows. This non-uniformity is substantially reduced by applying water in surges that saves 20 - 30% of the irrigation water. The post - advance phase aims at increasing the opportunity time at the furrows tail. Runoff water losses reach 30 - 40% of the delivered water when realizing continues furrow irrigation of high uniformity performances. Surge irrigation in post - advance phase could produce equivalent uniformity and reduce runoff to 10 - 15% of the total delivered water. Overlapping surges of short on/off - time during post-advance phase turn out continues opportunity time at the furrow tail that improves uniformity of water distribution over the furrow length. Automatic surge have been manufactured. The price of the latter is unreasonably high for the farming system in developing countries. Surge irrigation could be realized in such countries, including Bulgaria, by means of additional labor requirement instead of installment of automatic valves. Several surge irrigation technology have been tested and their description is provided in the full text of the report. On basis of the reported analytical and experimental research it is concluded that surge irrigation could save 30 - 45% of irrigation water required for continuous irrigation. Keywords: Advance uniformity, furrow irrigation, runoff, surge.- flow, water saving.
