PH Requirements 2026: Eligibility, Prerequisites & How to Qualify

Who Issues the Professional Hydrologist Credential

Professional Hydrologist (PH, sometimes written P.H.) is a credential awarded by the American Institute of Hydrology (AIH). It is not a state license, and it is a different credential from the Hydrologic Technician or Hydrologist-in-Training (HIT) designation, which AIH also administers at an earlier career stage. If you are new to the terminology, our explainers on what PH is and what PH certification involves cover the basics, and this article focuses on the practical question: do you qualify, and how do you get there?

One housekeeping point matters before anything else. AIH currently links both a 2026 and a 2024 version of its bylaws. The version approved on January 30, 2026 is the one linked from the AIH homepage and it controls. If you have an old PDF saved from a prior year, replace it before you plan your application. Eligibility details in the sections below come from Sections 3.2 and 3.4 of that 2026 document, with fees drawn from AIH's certification requirements and membership pages.

Education and Experience Requirements

The Professional Hydrologist pathway pairs a relevant degree with a stretch of qualifying post-degree hydrology experience. The higher your degree, the shorter the experience requirement:

Two phrases in that table deserve attention: "relevant" and "qualifying." The degree must be in a field relevant to hydrology, and the experience must be hydrology work performed after the degree was earned. Experience accumulated before graduation, or in an adjacent field with only incidental water content, is the most common place applicants run into trouble. If your job history is mixed, document specifically which projects involved hydrologic analysis, data collection, modeling or design, and be ready for AIH to evaluate that record.

The Coursework Checklist

This is where many otherwise-qualified candidates discover gaps. Beyond holding a degree, the bylaws require specific coursework hours, expressed in both semester and quarter units:

• Chemistry: five semester hours (eight quarter hours)
• Physics: five semester hours (eight quarter hours)
• Calculus: five semester hours (eight quarter hours)
• Basic hydrology: three semester hours (five quarter hours) in basic surface-water or groundwater hydrology
• Specialty coursework: 25 semester hours (40 quarter hours) in your specialty area

Chemistry, physics and calculus each carry their own hour minimum. Strength in one does not offset a shortfall in another, so audit all three separately against your transcript.

Category I and Category II specialty hours

The 25-semester-hour specialty block has an internal structure. At least 10 semester hours (16 quarter hours) must be Category I coursework. The remainder may be Category I or Category II. To see how a particular course is classified, consult AIH's Approved Coursework List, most recently updated September 14, 2026. Treat that list as a source of eligibility examples. It tells you what counts toward qualification; it is not an outline of what appears on the exam, and it should not be used as a study syllabus.

Referees and the Application

Applicants must provide three referees. These should be people who can speak credibly to your hydrology experience and professional character, so choose supervisors, senior colleagues or professional peers who have seen your technical work rather than casual acquaintances. Give them advance notice and your experience summary so their statements align with your application.

Applications are submitted through Certemy, AIH's application platform. A standard application fee of $100 applies. Building your application early is wise, because assembling transcripts, documenting years of experience and coordinating three referees takes longer than most people expect. For a fuller look at timing, see our guide to PH exam dates, windows and deadlines.

The Two-Exam Path: Part I and Part II

On the ordinary documented path, qualifying means passing two separate exams: a common Part I (Fundamentals) and one applicable Part II specialty. Published specifications for each are approximately 100 questions and four hours, so the total across both is roughly 200 questions and eight hours, but delivered as two separate exams, not one sitting. Part I is explicitly multiple choice, and AIH's practice and development materials also use multiple choice. The minimum passing score is 70% on each exam. AIH administers the exams with virtual proctoring, in English, and candidates may use open book, references, notes and calculators. Be aware that the relationship between the reference-computer rules and virtual delivery is not fully resolved in published guidance, so do not assume digital references are allowed; confirm before exam day. For score-level detail, see PH passing score explained.

Three failures bar further AIH applications, according to the examination page, which makes preparation quality matter from the first attempt. Our PH exam difficulty guide discusses what makes these exams demanding. Note that scored versus unscored question splits and an overall pass rate are not disclosed, so treat any figure you see quoted elsewhere with skepticism; our PH pass rate article explains what can and cannot be said.

Part I: Fundamentals

The common Part I draws on four headings:

Part II: Choose a specialty

Part II is where you commit to a specialty. Each specialty's weights total 100% on their own, so never add figures across alternatives. Here is how the two documented specialties compare:

The contrast is useful when picking a specialty. Surface Water leans most heavily on interpretation, analysis and modeling, while Groundwater puts its largest share on data collection and inventory. Choose based on your actual professional experience, since the experience record you submit should already point toward one of these directions. These percentages describe examination objectives, not a preparation curriculum. For the full breakdown of how the content areas fit together, see our PH exam domains guide.

What about Water Quality?

The current requirements and bylaws recognize Water Quality as a specialty, but we could not verify a current standalone Water Quality exam outline, weighting or timer. AIH's older examination-development page lists question-bank categories such as wastewater, limnology, aquatic chemistry, microbiology, soils and sediment, and pollutant fate and transport, but those are historical development categories, not confirmed current exam objectives. If Water Quality is your intended specialty, contact AIH for current guidance before building a study plan around any category list.

Holding a HIT Credential First

If you already hold a valid Hydrologist-in-Training credential, you do not repeat Part I. The Fundamentals exam is the shared component, so a current HIT holder moves directly toward a Part II specialty, and the Part I requirement is not an additional step on top. This makes HIT a sensible early-career stepping stone: you can pass Fundamentals while still accumulating the years of experience the PH bylaws require.

Fees and Ongoing Costs

The $500 initial total is a calculation from the standard published fees and excludes dues. AIH does not label the amounts as USD, and no general member versus non-member exam fee pair is published. Organizational-affiliate discounts may exist but are conditional, so ask whether your employer or society qualifies. For a deeper look at budgeting, read our PH certification cost breakdown, and if you are weighing the investment, is the PH worth it? and the PH salary guide address the return side.

Maintaining the Credential

Qualifying is only the first stage. Active status involves annual dues of $175, a $65 recertification fee every five years, and continuing professional development. Here the published guidance contains an unresolved inconsistency you should plan around:

• AIH's requirements page states at least 12 PDH/PDC annually, with documentation each December 31.
• AIH's continuing-education guidance page describes 60 over five years, with submission by December 31 of year five.

Do not read the five-year guidance as a waiver of the stated annual requirement. The safest approach is to log 12 qualifying hours every year and keep documentation current, which satisfies both readings. Recertification is required alongside annual dues, not instead of them.

Sequencing Your Prep Around the Requirements

Because the requirements shape what you need to do and when, a sensible order of operations looks like this:

For a deeper preparation plan, see the PH study guide, and when you are ready to test yourself on realistic questions, the PH practice test is a good place to check where you stand. A quick-reference review is also available in the PH cheat sheet, and you can run another set of practice questions on the main practice site.

Frequently Asked Questions