Eight-year (2000-2007) field studies on the effectiveness of controlled drainage in loam sandy soil were carried out in the Lowland of Middle Lithuania. The plot, which has existing subsurface water removal systems operated as conventional drainage was readjusted for the water table management. Two separate systems - 4.9 hectares free drainage (FD) and 5.4 hectares controlled drainage (CD) were arranged. A water level control structure with a riser column and hand operated rigid flap door was installed in the outlet of drainage collector in the manhole at the junction of two collectors. The water table level was allowed to rise to the maximum of 68 cm above the drains. Measurements to record the water table depth, drain outflow quantity and quality were performed. It was determined that in the CD system the annual drainage outflow lasted shorter by 40-62%, at the same time it was reduced by 25% and nitrate leaching - by 20-28% lower in comparison with the drainage operating in an ordinary regime. These indicators varied depending on weather conditions. The water table control in single-acting drainage systems is feasible and has a positive hydrological and environmental impact.

Peat is still mined in many parts of the world for production of peat substrates and energy. Many peatlands were affected by drainage in the past also for forestry and agricultural needs. Nowadays a raised attention to peatlands is focused, especially to drained peatlands due to their carbon reserves and their potential influence to the climate on the one hand, but on the other hand - due to raising awareness on protection of environment, habitats and biotopes. There are many examples on restoration activities in peatlands found worldwide, especially their water regime is the subject of regulation, which plays the major role to bring back original functions. In most cases in Latvia as the aim for protection and restoration of degraded peatlands was protection of EU biotopes and habitats. Of course, peatlands play an important role in emissions of the greenhouse gases CO2, CH4 and N2O, produced during mineralization of the drained peat organic matter. In literature, we can find only few cases where hydrological regimes are described for natural raised as well as restored block-cut peat extraction fields. This research analyses block-cut peat extraction field water level fluctuation influence on naturally raised bog hydrological regimes. Hourly data is analysed for six groundwater monitoring wells as well as for determination needs of water level fluctuations in excavated peat quarry as a response to precipitation.

Forest drainage is a common management practice, carried out in order to improve tree growth; however, the alterations in hydrological and microclimate dynamics can cause diverse changes in the characteristics of ground cover vegetation. The aim of study was to characterise the composition and richness of ground cover vegetation in drained forest stands, where the groundwater levels have been affected by the reconstruction of drainage diches. Research was conducted in the hemiboreal forests of Latvia. Three study sites were chosen, measurements of groundwater level, stand parameters and projective cover of ground covered vegetation took place in two stands which underwent reconstruction and restoration of the drainage system in 2019, and a control stand, where the drainage system had not been restored. For assessing the relationship of ground cover vegetation in relation to groundwater level and stand factors, DCA analysis was used. The differences between stands, regarding the species projective cover and species composition, were assessed by ANOSIM (Analysis of similarities). Sites, where drainage ditches were fully or partially reconstructed exhibited a greater diversity of ground cover vegetation species compared to the control stand, where no renewal of drainage ditches had occurred. Conversely, the control stand displayed a higher projective cover of the bryophyte layer. The composition of ground cover vegetation species differed amongst all studied stands, the varying stand characteristics and co-dominant tree species in canopy layer had a more pronounced influence on ground cover vegetation, making it complicated to evaluate direct impact of groundwater level.