Reconstruction of springs discharge using tree-rings and earlywood vessel chronologies in an alluvial aquifer

Abstract

Abstract Monitoring changes in groundwater storage is necessary for water resource management plans. The temporal records of spring discharge are restricted by the absence or paucity in many parts of the world. To address this shortcoming, various models and methods have been implemented to reconstruct past hydrologic data. In this study, temporal variations of spring discharge were reconstructed using tree-rings and earlywood vessel chronologies in an alluvial aquifer on the southern coast of the Caspian sea. The dendrochronological analysis was performed using both cross-sections and core samples of Zelkova carpinifolia (Pall.) K. Koch species, including tree-rings width and vessel features (vessels diameter, area, and perimeter) as proxy data. The distance between the sampling trees varied between 20 and 1000\xa0m. An artificial neural network (ANN) was used to establish a relationship between the temporal dendrochronological records of Z. carpinifolia and corresponding discharge obtained from two alluvial springs in the vicinity of sampling trees. The ANN model was optimized and tested by comparing the recorded and predicted values in the training and testing stage of the modeling process. Results show the high performance of the ANN model in the training (R-squared\xa0=\xa00.98, MSE\xa0=\xa00.009) and test stage (R-squared\xa0=\xa00.81, MSE\xa0=\xa01.26). The results also indicated the higher correlation of springs discharge with vessel features (R\xa0=\xa00.76) compared to tree-rings (R\xa0=\xa00.59). Dendrohydrology works better for those springs with notable discharge changes during the growing seasons. Further, the combination of tree-ring width and vessel features as inputs in modeling will increase the model s performance. The tested model was applied to the dendrochronological records of past decades (1982 to 2001) to reconstruct the spring discharge data during the growing seasons for those years.