EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Solving the 23 Major Mysteries in Hydrology: Who Cares and Why?

Daniel Loucks
Daniel Loucks
  • Cornell University, Civil & Env. Engrg., Ithaca NY, United States of America (

A recent paper (Bloeschl, et al. 2019) reported on the outcome of a multi-year effort involving over 200 scientists identifying the 23 most unsolved scientific issues facing the hydrologic community today.  The purpose of this exercise was to motivate the hydrologic research community to focus their work on these issues to better understand the major causes of how water behaves in our catchments, watersheds and river basins, often in different ways at various space and time scales, and under the influence of various degrees of human interactions. Aside from the scientific value that this increased understanding might bring, this presentation focuses on two questions: Why and how might this increased understanding be beneficial and who would benefit? In other words, who should care and why? This interactive presentation attempts to provide some answers to these two questions for each of the 23 identified unsolved scientific problems. But in general it is clear much of the impact that humans are having on our environment is driven by how the hydrologic cycle fits in with the needs of humans and our supporting ecosystems. Water in our environment affects the spread of contaminants and pathogens, the energy and food and industrial goods we produce, the ecosystem services we enjoy, and the duration and extent of floods and droughts some endure. Understanding these links and their economic, health, and social consequences will allow us to manage our water resources and their use more effectively, and perhaps even reduce the risks of reaching tipping points that could forever change how we all will live and survive in the future.    

How to cite: Loucks, D.: Solving the 23 Major Mysteries in Hydrology: Who Cares and Why? , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-364,, 2019


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displays version 1 – uploaded on 21 Apr 2020
  • AC1: Comment on EGU2020-364, Daniel Loucks, 03 May 2020

    Here are some possible questions to address if we run out of things to talk about and still want to talk.


    How can addressing any or all of these 23 hydrologic issues help us better manage problems such as:

    • The adverse impacts of the current droughts in in over much of Australia and South Africa, Southern and western US, and parts of South America and Europe.
    • The unsustainability of water supplies of many urban centers such as London, Delhi, Barcelona, Tokyo, Lima, Tehran, Kabul, Amman, Karachi, Istanbul, Moscow, Cairo, Sao Paulo, Bangalore, Chennai, among others.
    • Low water levels in the Mekong affecting food production and security in Cambodia and Vietnam and low flows in the Rhine affecting shipping and the economy of central Europe.
    • Degradation of the quality of water in the North American Great Lakes among many other lakes along with coastal waters due in part to human activities and climate change.
    • Flood damage to coastal roads, marinas, and household property bordering U.S. Great Lakes and throughout much of the United Kingdom, for example.
    • Spread of diseases such as cholera and diarrhea in Yemen from excessive rain.
    • Spread of Covid-19 worldwide. How water connects to the coronavirus pandemic. 
  • AC2: Summary of 364 AC, Daniel Loucks, 04 May 2020

    Summary:   UPH:   Who cares and why? 

    The 23 unsolved problems in hydrology (UPH) involve:

    • Variability and Uncertainty and Non-stationarity in time and space that play a major role in
      • o Infrastructure design and operation (including urban stormwater management).
      • o Land use, watershed, and water quality management.
      • o Ecosystem functioning, water supply management.
    • Hydrology Interfaces
      • o Seawater – groundwater –surface water interactions and management
      • o Surface runoff management
      • o Impact on and impacted by human – social systems
    • Measurements, Data
      • o Infrastructure siting and design
      • o Use of cost effective and reliable sources and techniques
    • Modeling Methods
      • o Adaptive to given needs, data, time available, uncertainties, social and political systems.
    • Interface with Society ( Humans )
      • o Meeting changing needs of society
      • o Interacting with food and energy sectors
      • o Public health and welfare