President’s Corner – Summer 2023

The future of the American Institute of Hydrology is bright! We’ve experienced some amazing membership growth in 2023 and now we’re up to nearly 500 members. One of our most promising statistics is our growth in student membership! I can’t wait to engage our students as they explore career options and make sustainable contributions to hydrology, and I look forward to the continued growth of our organization.

In this issue of our Bulletin, you’ll be learning more about our growing webinar series, our first ever Diversity, Equity and Inclusion Scholarship Program, our on-going collaboration with sister organizations like SEDHYD, and some cutting-edge studies conducted by prominent hydrologists.

AIH thrives because of volunteer members like you! Here’s the latest on our committee activities, and some specific ways your participation is critical to our success:

        Get involved with our DEI Committee and help launch our first AIH Scholarship Program. We need your help developing the scholarship application process and criteria, as well as developing a robust outreach program to students interested in pursuing higher education in hydrology. With so many new student members, the competition will be fierce, but exciting (Contact co-chair Matt Naftaly at to join).

        On June 29, please attend our 4th webinar of the year, titled “Investing in People to Achieve Clean Water Goals”, by Jenny Seifert! Join the Webinar Committee and help guide the future of our webinar series, including new opportunities to sponsor webinars (Contact Committee Chair Luciana Cunha at to join).

        Join the Board of Registration and help us administer our certification process (Contact BOR Chair Nick Textor at to join).

        Join the Communications Committee and help curate articles for our Bulletin, and content for our website (Contact Brennon Schaefer at to join).


Still not sure where to get started or have an idea for a new committee? Drop me a line at I’d love to hear your ideas on how to make AIH your professional home for hydrology!

2023 Webinars: the latest and greatest

In 2023, AIH continues to serve its members with free webinars. Hot topics include the state of science research, operational hydrology, the history of hydrology and AIH, and trends in the field. This year, Glenn Moglen presented the Sensitivity of the NRCS Curve Number to Calibration Methods, Luciana Cunha discussed the Next Generation Water Resources Modeling Framework being developed by NOAA, and Roman Kanivetsky told us stories about founding AIH and exposed AIH members to an in-depth and enlightening discussion on Water Sustainability. We have much more to come. In June, Jenny Seifert will discuss the need to invest in People to Achieve Clean Water Goals. In July, we will start a series on flood forecasting, monitoring, and mitigation.

AIH is happy to offer those in good standing the opportunity to sponsor AIH webinars. For more information, please contact Luciana Cunha at

AIH DEI Scholarship Fund

The AIH Diversity, Equity, and Inclusivity Committee has landed on an exciting priority initiative: the DEI Scholarship Fund. Since beginning its work early in 2022, the DEI Committee has developed several initiatives to further its goal of extending educational and professional opportunities to those not commonly represented in hydrology-related fields. These initiatives include:

  • An International Mentorship Program
  • Minority Serving Institutions Outreach
  • An AIH Speakers Bureau
  • A Hydrology Job and Career Portal

Approved by the AIH Board of Directors at the May 23rd Meeting, the DEI Scholarship Fund will make funding available to selected individuals for hydrology-related training or education. As part of its action, the Board approved seed money for the Fund from revenue collected by the AIH Career Center, an on-line AIH service for advertising job opportunities. It is anticipated that additional revenue for the Fund will come from voluntary AIH membership contributions and corporate sponsors.

There is much to be done!

The DEI committee invites your participation in committee activities including development of the Scholarship Fund and the other DEI initiatives. With the Scholarship Fund being approved by the AIH Board of Directors, it’s time for the DEI Committee to get busy developing the details of implementation including program criteria and management, recipient selection, funding sources, and program outreach. The goal of the DEI Committee is to start awarding funds in 2026.

To join the AIH DEI Committee, or for additional information on the Scholarship Fund and other DEI Committee initiatives, contact Committee Co-Chairs Matt Naftaly at or 805.308.8529 or John Ramirez at or 662.325.9885.     


AIH was a proud Silver-Level Sponsor and Exhibitor at the 2023 Federal Interagency Sedimentation and Hydrology Modeling Conference (SEDHYD), May 8-12, 2023, in St. Louis, Missouri. The conference is held every 4 to 5 years and brings together engineers and scientists from federal agencies, universities, and consultants with a focus on watersheds, stream channels, reservoirs, and related infrastructure. Jamil Ibrahim (Immediate Past-President) represented AIH at the conference to staff the AIH booth, discuss benefits of students earning early certification as Hydrologists-in-Training (HITs) at the Student Luncheon, and share organizational and individual perspectives during a Diversity, Equity, Inclusion, Accessibility breakout session. There were several AIH members in attendance, including: Laura Keefer, PH (Member, Board of Registration); Dr. Jim Selegean, PH; Dr. Marty Teal, PH, Dr. David Williams, PH (Former Chair, Board of Registration), and. Dr. Zhong Zhang, PH (Director, Academic Affairs).

This was the first time SEDHYD had sponsors for their conference. In 2019, SEDHYD organizers graciously provided AIH an exhibit booth and dedicated time during the conference’s opening plenary to introduce AIH and benefits of certification for hydrologists and hydrologic technicians, and present AIH’s 2019 awards. Over 400 hydrologists, engineers, and scientists from across the U.S. attended the conference. AIH looks to maintain a strong connection to the SEDHYD community and actively support future SEDHYD conferences.

A Climate Condition Analysis Using Palmer Hydrologic Drought Index (PHDI) values

A Climate Condition Analysis Using Palmer Hydrologic Drought Index (PHDI) values

Richard Koehler, PhD, PH, CEO, Visual Data Analytics, LLC



Drought and climate change are important factors to include in any hydrologic analysis. Current weather-related events in California, such as the extended drought and recent multiple atmospheric rivers, demonstrate how quickly hydrologic conditions can change. A lag(1) autocorrelation analysis of California Climate Division 2 (Sacramento Drainage) using monthly Palmer Hydrologic Drought Index (PHDI) values was conducted to find data ranges, persistence of conditions, along with seasonal and historical drought patterns. Results show distinct conditions within the hydrologic-climatic system which include periods of (a) persistent drought, (b) persistent wet, (c) transition from drought to wet, and (d) transition from wet to drought. Month-to month PHDI changes are quantified using a summation infographic based on the autocorrelation scatterplot.

Key words: PHDI, drought, lag(1) autocorrelation



California is divided into seven climate divisions, each with various types of climate indices (Figure 1). For this study, Climate Division 2, Sacramento River drainage (NOAA, 2023a) is used as it contains the Lake Shasta reservoir, an important component of California’s water resources system.

This study examined PHDI information produced by NOAA’s National Centers for Environmental Information (NCEI). The NOAA website for drought data states that the PHDI “measures hydrological impacts of drought (e.g., reservoir levels, groundwater levels, etc.) which take longer to develop and longer to recover from. This long-term drought index was developed to quantify these hydrological effects, and it responds more slowly to changing conditions than the Palmer Drought Severity Index” (NOAA, 2023b). Table 1 describes the different PHDI levels (Hayes, 2007) and Figure 2 shows the 1895 to 2023 timeline plot of this monthly data  (NOAA, 2023c).

Some of the most severe drought values have occurred in recent years, with June 2021 through September 2021 all exhibiting PHDI values in the extreme drought range (-5 or more negative).

Figure 1: California Climate Divisions,

Climate Division 2, Sacramento River drainage (source: NOAA).

Table 1: PHDI level descriptions (Hayes, 2007).

Figure 2: California Climate Division 2,  monthly PHDI values, 1895 to 2023 (source: NOAA).

A histogram (Figure 3) shows the number of months for each PDHI value. There is a distinct bimodal distribution, with a total of 804 months of drought conditions (negative PHDI) and 661 months of wet conditions (positive PHDI). The 0 condition (near normal) represents only 15 months, indicating that this rarely occurred.

Figure 3: California Climate Division 2,  PHDI histogram – months per PHDI condition.

Analysis technique

A lag (1) temporal autocorrelation scatterplot was used to examine the PHDI data. Table 2 shows the one-month data shift used to create an x-y system with PHDI at time “t” for the x coordinate,  and PHDI at time “t+1” for the y coordinate.

Table 2: PHDI one-month data shift example.


Extremes can be represented by large positive and large negative monthly PHDI changes, shown in the following tables (Tables 3 and 4).

Table 3: Ranked largest positive monthly PHDI changes, California Climate Division 2.

Table 4: Ranked largest negative monthly PHDI changes, California Climate Division 2.

However, this simple approach provides an incomplete view of how the hydrologic-climatic system operates. A more expansive approach is to graph all monthly changes with a lag(1) autocorrelation scatterplot (Figure 4), where each point represents the monthly PHDI change.

Any point on the dashed diagonal line (y = 1x) indicates no PHDI change from month-to-month. Any point above the diagonal line signifies positive PHDI changes, while any point below the diagonal line signifies negative PHDI changes. Additionally, the overlay shows groups of points that represent four components of the hydrologic-climatic system, (a) persistent drought, (b) persistent wet, (c) transition from drought to wet, and (d) transition from wet to drought. The Table 1 description for “near normal” (-0.49 to +0.49) rarely happened, as the hydrologic system constantly oscillates between persistent drought and persistent wet conditions.

Figure 4: PHDI lag(1) autocorrelation scatterplot with four conditions.

As each point can be identified by month, a breakout of seasonal scatterplots is possible as shown in Figure 5.

Spring and summer have fewer transitions. These two seasons also have less overall scatter, indicating more persistent wet and dry conditions. Interestingly, summer has both the driest and some of the wettest PHDI values. Winter and fall show more randomness, as data points are more scattered. These two seasons also have more transition points. Atmospheric rivers typically occur during winter (NASA 2023) but, with transition points seen in all four seasons, other mechanisms are likely in play.

Figure 5: Seasonal autocorrelation scatterplots, (a) winter, (b) spring, (c) summer, (d) fall.

PHDI values were rounded to the nearest 0.5 to provide a consistent way to compare all month-to-month pairings, allowing for a summation of all changes for the period of record: 1895 to 2023 (Figure 6).

The PHDI value of -3 shows the single greatest range of change, -4 to +2.5 (Figure 6a). This display helps identify the most and least common changes that have taken place. The most common value is the monthly PHDI value of -1.5 followed by -1.5, which occurred 81 times (Figure 6b). Summation values of 1 indicate unusual conditions as these specific monthly changes occurred only once in the 128-year record.

Figure 6: Historical summation of all PHDI monthly changes for California Climate Division 2:

(a) single largest change, (b) most common month-to-month occurrence.

Coordinates for count values are based on categorized PHDI values.


The lag(1) autocorrelation scatterplot provides a basis for additional information about climatic datasets not possible with other methods. The identification of four distinct components of the hydrologic-climatic system provides new opportunities for planning and management activities by water resource organizations. The success of this approach suggests that more research should be directed to looking into mechanisms that enable large PHDI changes.

For more information about the Lag-1 autocorrelation, please read Dr. Koehler’s previous article, titled “The Lag-12 Hydrograph – Alternate Way to Plot Streamflow Time-Series Data”, AIH Bulletin, Fall 2022.



Hayes, M. J., 2007. Drought Indices.

NOAA, 2023a. Location of US Climate Divisions.

NOAA, 2023b. Historical Palmer Drought Indices.

NOAA, 2023c. Climate at a Glance Divisional Time Series.

NASA, 2023. Atmospheric Rivers


About the author

Dr. Koehler is the CEO of Visual Data Analytics and a certified professional hydrologist with over 40-years’ experience.

Previously he was the National Hydrologic and Geospatial Sciences Training Coordinator for NOAA’s National Weather Service and is a retired NOAA Corps lieutenant commander. Assignments included navigation and operations officer for two NOAA oceanographic research ships, the Colorado Basin River Forecast Center and the Northwest River Forecast Center, where he oversaw the implementation of an operational dynamic wave model for Lower Columbia River stage forecasts. Other positions include Director of Water Resources for an Arizona consulting company and the water resources hydrologist for Cochise County, Arizona.

He is also a member of the science department faculty at Front Range Community College and is instructor for astronomy, geology, geography, GIS and geodesy courses. He is also an FAA certified professional drone operator.

He has a PhD, MS and BS in Watershed Management from the University of Arizona and an additional MS in Hydrographic Sciences from the US Naval Postgraduate School. The focus of his research are alternate methods of analyzing environmental time-series data along with associated data visualizations.

Comparison of meshless MFS and CVBEM computational methods in analysis of groundwater flow pathways

Comparison of meshless MFS and CVBEM computational methods in analysis of groundwater flow pathways


Saleem Ali1, Sebastian Neumann1, T. V.
Hromadka, II2, B. Wilkins3
Cadet, Dept Mathematical Sciences, USMA, West Point, NY1
Distinguished Professor, USMA, West Point, NY2
Columbia University3

Introduction and Methodology

Computational methods to solve groundwater contamination problems continue to be of high interest to engineers and planners, among others. An important problem is identifying the source of contamination within a cluster of candidate sources. A key question is which candidate source(s) are the actual point source of the subject contamination.

About the author

Saleem Ali is a mathematical sciences major at the United States Military Academy, who is majoring in mathematical sciences. His research experience includes the computational modeling of ideal fluid flow and studying the effects of time dilation in balloon satellite flight.

Congratulations to our 2023 AIH Award Winners!

Founder’s Award:

Dr. John Nieber – P.H., P.E., Ph.D

Professor at the University of Minnesota in the Department of Bioproducts and Biosystems Engineering

Charles V. Theis Award for Groundwater:

Dr. Ken Howard – PHG, PGeo, FGC, CGeol FGS, PhD.

Professor at the University of Toronto Scarborough in the Department of Physical and Environmental Sciences

Ray K. Linsley Award for Surface Water:

Dr. Jeff McDonnell – P.H., FRSC, Ph.D.

Professor at the University of Saskatchewan in the School of Environment and Sustainability, and Associate Director at the Global Institute for Water Security.