Investigation of the groundwater level dynamics in the rice system under different parameters of irrigation and drainage network

Abstract The dynamics of groundwater level formation on two types of rice irrigation plot were studied: “rice irrigation plot with an irrigator-discharge in a notch and with drainage channels CCD” and “rice irrigation plot with an irrigation channel in an embankment and with drainage-discharge channels (KTC)” with various design parameters of the drainage network. On the basis of long-term field observations of the groundwater level (GWL) lowering on the CCD and KTC with use a network of observation wells, differences in the intensity and uniformity of drying of these types of rice irrigation plots in the pre-harvest and inter-vegetation periods have been established. It has been established that a more favourable water-air regime takes place in the rice irrigation plots CCD with different parameters of the drainage network compared to the rice irrigation plots KTC. At CCD, due to the draining effect of the irrigator-discharge, the field dries out more intensively after the water discharge process. This allows the rice harvest to be carried out in an optimal and rather short time. The presence of the irrigator-discharge as the element of the CCD allows to supply and divert water in a short period of time, evenly over the entire area as well as to perform the role of shallow drain and contribute to intensive drying and desalination of soils. It has been established that the yield of rice on CCD higher than on KTC with the corresponding parameters (on average 400-500 kg·ha −1 ). It has been established that due to these advantages, the rice yield on the CCC the inter-drainage distance 200 m and 250 m is on average 5-7 centner·ha −1 higher than on the KTC with the same parameters, and higher than on the CCD with the inter-drainage distance 500 m on 17 centner·ha −1 .