Assessment of dependence of change in Lithuanian river runoff on size of drained areas

Мисецкайте О., Тапараускене Л. Оценка зависимости изменения стока рек Литвы от размера осушенных территорийFollowing 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 flow coefficient of the whole 10th hydrologic region of Lithuania was 0.3 till reclamation. It decreased to 0.28 during the period of intensive rec-lamation, however, the average annual flow was 0.35 from 1980, i.e., it increased in comparison with the period till reclamation. The average flow 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 flow coefficient increased – 0.11

COMPARISON OF WATERMARK SOIL MOISTURE CONTENT WITH SELYANINOV HYDROTHERMAL COEFFICIENT

Agricultural producers to determine irrigation scheduling practices for crop‘s waterrequirement better when the soil water content of their fields is known. SelyaninovHydrothermal Coefficient (HTC) coefficient is used for identifying droughts duringthe active vegetation period, based on the water balance equation. For farmers tomake measurements of soil moisture is simply with humidity sensors, for exampleWatermark type. Soil humidity values established using Watermark type humiditysensors, value interpretations are based on manufacture indications, however theyhave not been adapted to Lithuanian conditions. Soil moisture was measured withWatermark soil moisture sensors placed at 20 and 50 cm depths. After analysingthe values taken throughout the whole period and summarizing the results it hasbeen identified that plant growth condition period evaluation according to HTC andfactual soil humidity reserves (W) differs by 20%. HTC meaning dependenciesduring vegetation period using Watermark measured humidity, strong or averagelystrong interrelation is determinate, in most cases – statistically significant. Whenevaluating soil humidity reserves based on soil texture, it is recommended to keepthe critical Watermark level in light texture soil (sands) at 80 cbar, and in all othertypes of soil - at 150 cbar. The results clearly indicate that soil composition couldbe factors limiting the success of identifying droughts in agriculture carried byWatermark type humidity sensors