The impact of land reclamationon river water balance

Abstract

Most of the regulated rivers are situated in the middle part of Lithuania. Approxrmately 90oh of all agricultural lands are drained in the basrn of Nevezis River. Following the data series of 62 years, it was determined that water balance of Nevezis basin is characterized by negative water balance during May-September due to higher evapotranspiration than average precipitation amount of the same period. It was stated that the average annual runoff coefficient of the whole l0" hydrologic region of Lithuania was 0.3 till reclamation. It decreased to 0.28 during the period of intensive reclamation, however, the average annual runoffwas 0.35 from 1980, i.e., it increased in comparison with the period till reclamation. The average runoff coefficient of warm period was 0.10 till reclamation, and remained the same during the period of 1956-1980, while the data of 1981-1995 show that the average runoff coefficient increased * 0.11. After assessing the meteorological conditions and soil water balance of basin of Nevezis River it mieht be stated that the primary reason of water lack in the basin is climatic conditions.