Stockholm Junior Water Prize vs Regeneron STS and ISEF

By Dr. Harman Brah, MD · Judge, California Science & Engineering Fair

The Stockholm Junior Water Prize is a water research competition judged mostly on a written paper, which one student or a team of two enters online through their state. Regeneron STS is a written application for seniors working alone, and ISEF can only be reached by winning at an affiliated science fair, where students present a board and answer judges’ questions.

One water project can be entered in all three. Whether yours can depends on who did the work, when the research happened, and how well you rewrite it for each format.

The three side by side

Stockholm Junior Water Prize (U.S.)

• Grades 9 to 12, and age 15 by August 1 of the competition year
• Water projects only
• One student, or a team of up to two
• You nominate yourself for your state competition by submitting a paper online
• Judged mostly on the paper

Regeneron Science Talent Search

• Students in their last year of high school
• Any field of research
• Individual work only
• An online application built around a research report of up to 20 pages, plus three recommendations and short essays
• The 2027 application closes November 5, 2026 at 8 PM ET

Regeneron ISEF

• Grades 9 to 12, and not yet 20 on or before May 1 before the fair
• Any field, across 22 categories
• One student, or a team of up to three
• No direct entry: students qualify by winning at an affiliated local, regional or state fair
• 2027 ISEF is in Los Angeles in May 2027

Paper-weighted vs board

The Water Environment Federation (WEF), which runs the U.S. competition, says it weighs the research paper “much more heavily than the poster presentation.” At the state level, a panel of water professionals reads the papers and, in some states, interviews students at science fairs.

At nationals, judges score six weighted criteria. Relevance carries the most weight: does the project take on a real problem in the water environment, and could it improve the environment or people’s lives? National judges also look at how well the student shows ownership and knowledge of the project in a video presentation.

Regeneron STS is also a written competition, and its report has the same 20-page ceiling as the national SJWP paper. But the STS application asks for much more than the paper: sections about the student, their activities and how they spend their time, recommendations from a teacher and a project mentor, and short essays.

ISEF and the county fairs that lead to it are different. Students stand at a board, and judges receive the official one-page abstract, no more than 250 words, digitally.

Dr. Brah judges at the California Science & Engineering Fair. In his experience, the conversation at the board decides close calls, and the student has to defend every choice without a script.

The practical takeaway: write the paper first. A strong board and a clear interview come more easily once the student has written out the full argument.

Team of two vs STS individual

This is the decision to make before any research starts.

The Stockholm Junior Water Prize accepts teams of up to two, and one member submits for both. California’s 2026 state winner was a two-student team from Lynbrook High School in San Jose.

ISEF rules, which affiliated fairs follow, allow teams of up to three. Membership generally cannot change during the research year, and every member must meet the eligibility rules.

Regeneron STS accepts only independent, individual research. A team project cannot go to STS, and it cannot be split into two individual entries afterward.

So two friends who share a water project can take it to their county fair and to the water prize together, but neither can enter it in STS. A team of three fits the fair, not the water prize.

State route vs county fair

The water prize skips the fair system. No science fair is required, and any eligible student can enter their state competition online.

In California, the state round is run by the California Water Environment Association. It received 42 submissions in 2026 and chose one state winner, plus a second and third place. Some local fairs also give regional water prize awards, but those winners still submit their paper online for the state round.

In the 2026 cycle, state entries were due April 15, 2026, and state winners were announced online in the first week of May. The 2027 dates were not posted as of late October 2026.

ISEF works the other way. In California, students reach the state fair through the affiliated fair for their county, and that county fair is the only one authorized to qualify its schools’ students.

Bay Area dates for the 2026-27 year:

• Synopsys Science & Technology Championship (Santa Clara County): final application deadline for new participants January 8, 2027; championship March 4, 2027. Its grand prize winners qualify for Regeneron ISEF.
• Alameda County Science & Engineering Fair: judging March 13, 2027 at Chabot College. It is affiliated with both the state fair and Regeneron ISEF.
• San Mateo County STEM Fair: held virtually on March 20, 2027.
• Contra Costa County Science & Engineering Fair: held each March; the 2027 date is not posted yet.
• California Science & Engineering Fair: held in April; the 2027 date is not posted yet.

Regeneron STS has no route at all. Students apply directly through the online system.

How one water project can go to all three

The cleanest case is a senior working alone. For that student, the sequence for 2026-27 looks like this.

1. Before the experiment. Check whether the project needs pre-approval. Water projects that survey people or handle certain biological agents need review before work begins, and Synopsys sets pre-approval deadlines of November 2 and November 13, 2026. A survey started before approval cannot be entered at the fair.
2. Fall. Submit the STS application, with its 20-page report, by November 5, 2026.
3. Winter. Apply to the county fair, cut the abstract to 250 words or fewer, and build the board.
4. March. Present at the county fair.
5. Spring. Rework the paper for the water prize state round.
6. May. State water prize winners are named, and ISEF takes place for students who qualified.

Two fair rules shape the plan. For 2027, the research must fit within 12 continuous months, starting no earlier than January 2026. And work done anywhere other than home, school or the field, such as a university or community lab, needs an extra form displayed at the booth.

Rewriting the paper for the water prize

An STS report and a water prize paper share a length limit, but they are not the same paper. The national guidelines ask for an abstract of no more than 180 words, numbered conclusions, a short biography, and acknowledgements that state clearly how much outside help the student had.

The Discussion needs the most work. The guidelines say judges read it closely: what the results mean for the water problem, how new they are, how they compare with other researchers’ results, and whether a local agency or community could use them.

The guidelines also warn against stopping at the problem. A survey of an algae-choked lake alone will not rank highly; explaining the causes and how monitoring could improve management makes it stronger.

If the student is not a senior, or works in a pair

A junior, or a team of two, can enter the county fair and the water prize this year. STS accepts research done in any year of high school, so a junior working alone can still bring the same research to STS as a senior.

If that student goes back to the fair the next year with the same work, ISEF’s continuation rules apply. The new entry has to show a substantive expansion of the earlier project; repeating the same question and method with a larger sample does not count.

The student does the work

All three competitions check this. The water prize judging criteria ask what help came from parents, teachers and professionals, and whether the student took the measurements. STS requires disclosure of all support with the research and the application. ISEF rules bar generative AI from writing the research plan, abstract or poster.

A mentor can push on the question, the statistics and the Discussion. The student runs the experiments, analyzes the data and writes every version of the paper, and judges can tell when that is not the case.

Our mentors help students plan one water project across the fair, the paper and the application, with the student doing the research and the writing. See our research mentorship, or read how Regeneron STS and ISEF differ.

FAQ

Can my child enter the same water project in the Stockholm Junior Water Prize and ISEF?

Yes. The water prize does not require a science fair, so a project shown at a county fair can also be written up as a paper and entered in the state round. Follow the fair’s rules from the start, including the 12-month research window and any pre-approval.

Can a team project go to Regeneron STS?

No. STS accepts only individual research, and a team project cannot be split into separate entries. A team of two can still enter the water prize, and teams of up to three can enter ISEF-affiliated fairs.

Which deadline comes first?

For a senior, STS comes first: November 5, 2026 at 8 PM ET. Bay Area fair applications follow in winter (Synopsys closes January 8, 2027 for new participants), and the water prize state round comes in spring. In 2026 it closed April 15; the 2027 date is not posted yet.

Which ISEF category does a water project go in?

It depends on the project. ISEF’s 22 categories include Earth and Environmental Sciences and Environmental Engineering, but choose by the project’s actual question and methods.

Does my child need a lab for these competitions?

Not necessarily. The water prize accepts any project that uses accepted research methods and statistics on real data, and home, school and the field are standard work sites under fair rules. Work in a university or community lab is allowed but needs an extra fair form.