This article comprises three independent commentaries about the state of ICON principles in hydrology and discusses the opportunities and challenges of adopting them. Each commentary focuses on a different perspective as follows: (i) field, experimental, remote sensing, and real-time data research and application (Section 1); (ii) Inclusive, equitable, and accessible science: Involvement, challenges, and support of early career, marginalized racial groups, women, LGBTQ+, and/or disabled researchers (Section 2); and (iii) an ICON perspective on machine learning for multiscale hydrological modeling (Section 3). Hydrologists depend on data monitoring, analyses, and simulations from these diverse scientific disciplines to ensure safe, sufficient, and equal water distribution. These hydrologic data come from but are not limited to primary (in-situ: lab, plots, and field experiments) and secondary sources (ex-situ: remote sensing, UAVs, hydrologic models) that are typically openly available and discoverable. Hydrology-oriented organizations have pushed our community to increase coordination of the protocols for generating data and sharing model platforms. In addition, networking at all levels has emerged with an invigorated effort to activate community science efforts that complement conventional data collection methods. With increasing amounts of data, it has become difficult to decipher various complex hydrologic processes. However, machine learning, a branch of artificial intelligence, provides accurate and faster alternatives to understand different biogeochemical and hydrological processes better. Diversity, equity, and inclusivity are essential in terms of outreach and integration of peoples with historically marginalized identities into this professional discipline and respecting and supporting the local environmental knowledge of water users.

The National Ecological Observatory Network (NEON)’s standardized monitoring program provides an unprecedented opportunity for comparing the predictability of ecosystems. To harness the power of NEON data for examining environmental predictability, we scaled a near-term, iterative water temperature forecasting system to all six conterminous NEON lakes. We generated 1 to 35-day ahead forecasts using a process-based hydrodynamic model that was updated with observations as they became available. Forecasts were more accurate than a null model up to 35-days ahead among lakes, with an aggregated 1-day ahead RMSE (root-mean square error) of 0.60℃ and 35-days ahead RMSE of 2.17℃. Water temperature forecast accuracy was positively associated with lake depth and water clarity, and negatively associated with catchment size and fetch. Our results suggest that lake characteristics interact with weather to control the predictability of thermal structure. Our work provides some of the first probabilistic forecasts of NEON sites and a framework for examining continental-scale predictability.

Hydrologic sciences depend on data monitoring, analyses, and simulations of hydrologic processes to ensure safe, sufficient, and equal water distribution. These hydrologic data come from but are not limited to primary (lab, plot, and field experiments) and secondary sources (remote sensing, UAVs, hydrologic models) that typically follow FAIR Principles (FAIR Principles - GO FAIR (go-fair.org)). Easy availability of FAIR data has become possible because the hydrology-oriented organizations have pushed the community to increase coordination of the protocols for generating data and sharing model platforms. In addition, networking at all levels has emerged with an invigorated effort to activate community science efforts that complement conventional data collection methods. However, it has become difficult to decipher various complex hydrologic processes with increasing data. Machine learning, a branch of artificial intelligence, provides more accurate and faster alternatives to better understand different hydrological processes. The Integrated, Coordinated, Open, Networked (ICONs) framework provides a pathway for water users to include and respect diversity, equity, and inclusivity. In addition, ICONs support the integration of peoples with historically marginalized identities into this professional discipline of water sciences. This article comprises three independent commentaries about the state of ICON principles in hydrology and discusses the opportunities and challenges of adopting them.

Seasonal snowmelt pulses are the dominant hydrologic feature of most alpine catchments. The majority of annual export of water, carbon and nitrogen occurs within a short window of only a few weeks. This observation has largely been based on relatively infrequent manual sampling, and our understanding of responses to finer-scale variation, “pulses within the pulse”, is critically incomplete. Here, we combine high-frequency sensor measurements of dissolved organic carbon (DOC) and nitrate (NO3-N) with historical grab sample data from a high altitude stream in the Rocky Mountains of Colorado. We characterize the linkages between precipitation, snowpack, streamflow, and solute export, over time scales ranging from decades to minutes. At all time scales, discharge (Q) variation was several orders of magnitude larger than concentration (C) variation, making it the dominant control on solute flux rates. Interannual variation in Q, and by extension solute export, appeared correlated to the depth of the winter snowpack, and how late into the spring the snowpack persisted. Seasonally, we observed clockwise C-Q hysteresis, with solute stores becoming depleted as the melt pulse proceeds. Using the sensor data however, we were able to observe individual events. In contrast to the seasonal patterns, these events enriched concentrations, suggesting the persistence of additional DOC and NO3-N stores which can be mobilized within, and even after the main seasonal snowmelt pulse. The historical data suggest that reduced snowpack and earlier snowmelt in the coming decades may result in reduced export of DOC and NO3-N. The sensor data however make this conclusion uncertain, as rain on snow events, which are expected to become more prevalent, appear equally capable of mobilizing solutes.