Tree Ring and Climate Information based Reconstruction of Streamflow for Sacramento River, California

Abstract:

Tree Ring Chronology (TRC) is traditionally used for streamflow reconstructions. These reconstructions are helpful in understanding the dynamics of past flow conditions, including droughts and floods, by extending the length of available streamflow data. This study aims to improve the traditional reconstruction methodology that only uses TRC, by incorporating the climate index of Pacific Decadal Oscillation (PDO) and the Pacific Ocean Sea Surface Temperature (SST) information as predictor variables, along with TRC, in a stepwise linear regression model. The approach is tested on Sacramento River, in Southwest U.S., having a history of recurring hydrologic drought, coupled with the challenges of increasing water demands and changing climate. The proposed methodology is applied to four naturalized gages with the observed period of 94 years (1906-1998) to reconstruct streamflow dating back to year 1800, based on past climate information. Although selected TRC extend up to year 1378, the available climate information limits the reconstruction to year 1800. Results show that using the climate information of PDO and SST along with the TRC model, performance was better compared to the traditional reconstruction method using TRC only. These streamflow reconstructions can provide useful insights, to the regional water managers, about the duration and frequency of past hydrologic droughts, and help make informed decisions regarding water resources planning. For future studies, the improved reconstruction methodology, presented here, will be applied to other river basins in the region.