• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.149-149
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• 2022

Accurate quantitative evaluation of baseflow contribution to streamflow is imperative to address seasonal drought vulnerability, flood occurrence and groundwater management concerns for efficient and sustainable water resources management in watersheds. Several baseflow separation algorithms using recursive filters, graphical method and tracer or chemical balance have been developed but resulting baseflow outputs always show wide variations, thereby making it hard to determine best separation technique. Therefore, the current global shift towards implementation of artificial intelligence (AI) in water resources is employed to compare the performance of deep learning models with conventional hydrograph separation techniques to quantify baseflow contribution to streamflow of Piney River watershed, Tennessee from 2001-2021. Streamflow values are obtained from the USGS station 03602500 and modeled to generate values of Baseflow Index (BI) using Web-based Hydrograph Analysis (WHAT) model. Annual and seasonal baseflow outputs from the traditional separation techniques are compared with results of Long Short Term Memory (LSTM) and simple Gated Recurrent Unit (GRU) models. The GRU model gave optimal BFI values during the four seasons with average NSE = 0.98, KGE = 0.97, r = 0.89 and future baseflow volumes are predicted. AI offers easier and more accurate approach to groundwater management and surface runoff modeling to create effective water policy frameworks for disaster management.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.2
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• pp.1-11
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• 2017

The analysis of baseflow contribution is very significant in Korea because most rivers have high variability of streamflow due to the monsoon climate. Recently, the importance of such analysis is being more evident especially in terms of river management because of the changing pattern of rainfall and runoff resulted from climate change. Various baseflow separation methods have been developed to separate baseflow from streamflow. However, it is very difficult to identify which method is the most accurate way due to the lack of measured baseflow data. Moreover, it is inappropriate to analyze the annual baseflow contribution for Korean rivers because rainfall patterns varies significantly with the seasons. Thus, this study compared the baseflow contributions at various time-scales (annual, seasonal and monthly) for the 4 major river basins through BFI (baseflow index) and suggested baseflow contribution of each basin by the BFI ranges searched from different baseflow separation methods (e.g., BFLOW, HYSEP, PART, WHAT). Based on the comparison of baseflow contributions at the three time scales, this study showed that the baseflow contributions from the monthly and seasonal analysis are more reasonable than that from the annual analysis. Furthermore, this study proposes that defining BFI with its range is more proper than a specific value for a watershed, considering the difference of BFIs between various baseflow separation methods.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.317-317
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• 2018

Baseflow which is one of the unmeasurable components of streamflow and slowly flows through underground is important for water resource management. Despite various separation methods from researches preceded, it is difficult to find a significant separation method for baseflow separation. This study applied the MRC method and developed the improved approach to separate baseflow from total streamflow hydrograph. Previous researchers utilized the whole streamflow data of study period at once to derive synthetic MRCs causing unreliable results. This study has been proceeded with total nine areas with gauging stations. Each three areas are selected from 3 domestic major watersheds. Tool for drawing MRC had been used to draw MRCs of each area. First, synthetic MRC for whole period and two other MRCs were drawn following two different criteria. Two criteria were set by different conditions, one is flow condition and the other is seasonality. The whole streamflow was classified according to seasonality and flow conditions, and MRCs had been drawn with a specialized program. The MRCs for flow conditions had low R2 and similar trend to recession segments. On the other hand, the seasonal MRCs were eligible for the baseflow separation that properly reflects the seasonal variability of baseflow. Comparing two methods of assuming MRC for baseflow separation, seasonal MRC was more effective for relieving overestimating tendency of synthetic MRC. Flow condition MRCs had large distribution of the flow and this means accurate MRC could not be found. Baseflow separation using seasonal MRC is showing more reliability than the other one however, if certain technique added up to the flow condition MRC method to stabilize distribution of the streamflow, the flow conditions method could secure reliability as much as seasonal MRC method.

• Journal of Environmental Science International
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• v.15 no.3
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• pp.253-260
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• 2006

Groundwater recharge from precipitation is affected by the infiltration from ground surface and the movement of soil water. Groundwater recharge is directly related to the groundwater amount and flow in aquifers, and baseflow to rivers. Determining groundwater recharge rate for a given watershed is a prerequisite to estimate sustainable groundwater resources. The estimation of groundwater recharge rate were carried out for three subwatersheds in the Wicheon watershed and two subwatersheds in the Pyungchang River basin and for the period 1990-2000, using the NRCS-CN method and the baseflow separation method. The recharge rate estimates were compared to each other. The result of estimation by the NRCS-CN method shows the average annual recharge rate 15.4-17.0% in the Wicheon watershed and 26.4-26.8% in the Pyungchang River basin. The average annual recharge rates calculated by the baseflow separation method ranged 15.1-21.1% in the W icheon watershed, and 25.2-33.4% in the Pyungchang River basin. The average annual recharge rates calculated by the NRCS-CN method is less variable than the baseflow separation method. However, the average annual recharge rates obtained from the two methods are not very different, except NO. 6 subwatershed in Pyungchang River basin.

• Journal of the Korean Society of Groundwater Environment
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• v.7 no.1
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• pp.15-19
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• 2000

This study estimates the baseflow using the separation of daily streamflow hydrograph. For the separation of hydrograph, we used standard method. This method was presented by Institute of Hydrology in 1980. For the estimation of baseflow, we estimated the parameters of model using the relation of the catchment properties and the baseflow index. The baseflow is estimated by the results of the separation of daily streamflow hydrograph and is estimated 20.0%∼39.4%. Baseflow rates is high for larger catchments but low for smaller catchments. As the results of this study, there is no relation between rainfall and baseflow rates.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.135-135
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• 2022

In this study, we evaluated uncertainties in baseflow separation filter methods focusing on changes in recession constant (𝛼) values, which include Lynie & Holick (LH) algorithm, Chapman algorithm, Eckhardt filter, and EWMA filter. Here, we analyzed daily streamflow data at 14 stations in the Urmia Lake basin, Iran, from 2015 to 2019. The 𝛼 values were computed using three different approaches from calculating the slope of a recession curve by averaging the flow over all seasons, a correlation method, and a mean value of the ratio of Q_t+1 to Q_t. In addition to the 𝛼 values, the BFImax (maximum value of the baseflow index (BFI)) was determined for the Eckhardt filter through the backward filter method. As results, it indicates that the estimated baseflow is dependent upon the selection of filter methods, their parameters, and catchment characteristics at different stations. In particular, the EWMA filter showed the least changes in estimating the baseflow value by changing the 𝛼 value, and the Eckhardt filter and LH algorithm showed the highest sensitivity to this parameter at different stations.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.352-358
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• 2005

This study aims to separate hydrograph into baseflow and event water to calculate baseflow rate during a rainfall in small catchments, Yuseong, Daejeon, The hydrograph of stream during a period with no excess rainfall will decay. The discharge is composed entirely of groundwater contributions. During the period, the Cl concentration of the stream water can be regarded as being in equilibrium with that of the groundwater. Using Cl as a conservative tracer, two-component hydrograph separations were performed from end point of the period to next end point. The required data were obtained by monitoring of the surface water table, along with discharge rate of stream. Cl concentration of rainfall, surface water were measured and recorded. Hydrograph separation, a mixing model using chemical tracer is applied to chemical hydrograph separation technique. These results show that baseflow rates are 31.6% of rainfall in the catchments during study period.

• Journal of The Korean Society of Agricultural Engineers
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• v.58 no.1
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• pp.27-38
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• 2016

More severe and frequent flood and drought have increased the attentions on the river management. In particular, baseflow is an important element among many streamflow characteristics because streamflow is mainly consisted of direct runoff and baseflow. In this regard, this study attempted to analyze the relationship between streamflow variability and baseflow contributions on Nakdong river basin. For this, two Streamflow Variability Indices (SVI) were used: Coefficient of Variation (CV) and Coefficient of Flow Regime (CFR). Furthermore, baselow separation was individually conducted by three methods (PART, WHAT and BFLOW), and based on this, Baseflow Index (BFI) was calculated. Also, we used the daily streamflow data retrieved from 27 gauge stations in Nakdong river basin for baseflow separation. The results showed that BFI calculated by three models ranges from 0.14 to 0.90 for 27 gauge stations. For SVI, BFI has much higher correlation with CV than with CFR. Also, the inversely proportional relationship between BFI and CV showed that higher baseflow contribution, less streamflow variability.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.10a
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• pp.226-227
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• 2005

• Journal of Soil and Groundwater Environment
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• v.27 no.1
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• pp.50-59
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• 2022

There are several methods for separating the baseflow from the hydrograph, and graphical methods (GM) have mostly been used. GMs are those that separate the baseflow from the direct flow simply by connecting rising point with inflection point or points related to some duration from a hydrograph. Environmental tracer method (ETM) is another tool researched and developed under several conditions to estimate the groundwater recharge. The goal of this study is to separate the baseflow component from a storm hydrograph by applying various GMs and ETM, and to compare their results. The baseflow component estimated by ETM was different from the results by GMs in terms of their shapes of fluctuation and flow rates. Another important feature is that the form of the baseflow to which ETM is applied is similar to that of a storm hydrograph. This similarity is presumed to be due to the selection of tracer that respond quickly to rainfall.