Journal Article

Constructing Long‐Term Hydrographs for River Climate‐Resilience: A Novel Approach for Studying Centennial to Millennial River Behavior

Smith, Virginia, Hren, Michael T., Terry, Dennis O., Awadallah, Ayman G., Fernandes, Anjali M., Fathi, Mohamed M.

2024

Overview

Studying the centennial or millennial timescale response of large rivers to changing patterns in precipitation, discharge, flood intensity and recurrence, and associated sediment erosion is critical for understanding long‐term fluvial geomorphic adjustment to climate. Long hydrographs, maintaining reliable Flow Duration Curves (FDCs), are a fundamental input for such simulations; however, recorded discharge series rarely span more than a few decades. The absence of robust methodologies for generating representative long‐term hydrographs, especially those incorporating coarse temporal resolution or lacking continuous simulations, is therefore a fundamental challenge for climate resilience. We present a novel approach for constructing multi‐century hydrographs that successfully conserve the statistical, especially frequency analysis, and stochastic characteristics of observed hydrographs. This approach integrates a powerful combination of a weather generator with a fine disaggregation technique and a continuous rainfall‐runoff transformation model. We tested our approach to generate a statistically representative 300‐year hydrograph on the Ninnescah River Basin in Kansas, using a satellite precipitation data set to address the considerable gaps in the available hourly observed data sets. This approach emphasizes the similarities of FDCs between the observed and generated hydrographs, exhibiting a reasonably acceptable range of average absolute deviation between 6% and 18%. We extended this methodology to create projected high‐resolution hydrographs based on a range of climate change scenarios. The projected outcomes present pronounced increases in the FDCs compared to the current condition, especially for more distant futures, which necessitates more efficient adaptation strategies. This approach represents a paradigm shift in long‐term hydrologic modeling. Plain Language Summary River hydrographs are key inputs for understanding long term Earth surface processes. Due to the limited lengths of observational streamflow records, various techniques were previously developed with limited capabilities to generate representative long hydrographs. Through a novel integrated approach, we are able to construct robust high‐resolution hydrographs on multi‐century timescales, based on developing a linkage between hydroclimatic forces and watershed characteristics within a stochastic framework. We used this methodology to generate a 300‐year high‐resolution hydrograph with satisfactory correlation with the observed FDC. Due to the stochastic background of this framework, the deviation between the observed and generated FDCs was estimated to fall within a reasonable range of 6% and 18%. This framework was extended to provide hourly runoff projections for several future climatic models. Median projections for the near‐term period 2040–2069 demonstrated less deviation from reference data set compared to those for the more distant future 2070–2099. This study represents a scientific shift for long‐term simulations through re‐constructing past, simulating present, or projecting future hydrographs. Key Points Introducing a novel framework designed to generate statistically robust hydrographs on multi‐century timescales for long‐term simulations Integrating a weather generator and a disaggregation technique within a rainfall runoff model to achieve high‐temporal resolution hydrographs Utilizing multiple climate models to evaluate the impacts of climate change on hourly runoff responses

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: climate / Climate adaptation / Climate change / Climate change adaptation / climate change impacts (CMIP6) / Climate change scenarios / Climate models / data collection / Datasets / Deviation / Disaggregation / Discharge / Earth surface / Flow duration / Flow duration curves / flow duration curves (FDC) / Frequency analysis / Geomorphology / high‐resolution hydrograph / hydrograph / Hydrographs / Hydrologic data / Hydrologic models / Kansas / long‐term hydrograph / Precipitation / Precipitation data / Rainfall-runoff relationships / rainfall‐runoff transformation / Resilience / River basins / Rivers / Robustness / Runoff / Satellite observation / satellites / sediments / Simulation / Statistical analysis / Stream discharge / Stream flow / Temporal resolution / watersheds