Understanding water is at the heart of understanding environmental science. Water ties together many of earth’s natural cycles – and allows us to better understand the ways that humans interact and interfere with those cycles. From a legal standpoint, hydrologic science holds the key to understanding and interpreting multiple major environmental statutes, as well as caselaw involving takings law, tort law, natural resources law, and insurance law.

Cases involving water are likely to increase in the future, both as a result of communities’ increasing vulnerability to hydrologic-related disasters and as a result of evolving legal and statutory frameworks. The factors causing drought, flood, and water pollution are all exacerbated by human interference at local, regional, and even global scales. However, scientists are also developing innovative approaches to address these challenges, blending engineered and nature-based solutions to provide multibenefit solutions to ensure long-term sustainability.

The “Water and the Law” materials are designed to be accessed as needed rather than as course materials to be followed in a set order. They include three modules covering the three main areas of hydrological science:

1. Drought and Water Scarcity - Too Little Water
2. Flood: Too Much Water  
3. Water Quality: Polluted Water

Each of these three module addresses these questions:

• Why is an understanding of this issue important?
• How is the issue defined?
• What are its causes?
• How is it managed?

Sidebars within these modules provide further information.

• Science and the Supreme Court spotlights three U.S. Supreme Court cases in which the Court engaged with hydrologic science in reaching their ruling. 
• By the Books provides an overview of state law regarding surface water rights, the concepts of reasonable use and beneficial use of water, the doctrine of equitable apportionment in allocating ground water rights, law related to the capture of storm water on downstream water rights, and point-source versus non-point source contamination.
• By the Numbers describes common drought indices, techniques to map flood risk, and water quality indices.
• Zooming in on Mechanics discusses mechanisms important to understanding hydrology: positive and negative feedback loops, self-regulating systems, tipping points, bioaccumulation and biomagnification, and eutrophication.
• Cutting-edge Science showcases innovative tools and approaches that have reshaped the way hydrologists approach their work, including the use of satellites to track groundwater use, advances in flood forecasting and modeling, installation of green infrastructure to restore natural hydrology in mostly urban settings, and conservation buffers used for rural restoration.

A fourth module spotlights the U.S. Supreme Court’s ruling in County of Maui v. Hawaii Wildlife Fund to show how hydrologic science intersects with the law, and provides information on the science of groundwater.

Other materials include key takeaways regarding hydrological science; a selection of further resources; glossaries of acronyms and scientific terminology; and a list of cited caselaw.