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  visual.data.analytics@outlook.com

 

Abstract

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

 

Background

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.

Results

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.

Conclusions

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.

 

References

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

https://wwa.colorado.edu/sites/default/files/2021-09/IWCS_2007_July_feature.pdf

NOAA, 2023a. Location of US Climate Divisions. https://psl.noaa.gov/data/usclimdivs/data/map.html

NOAA, 2023b. Historical Palmer Drought Indices.

https://www.ncei.noaa.gov/access/monitoring/historical-palmers/overview

NOAA, 2023c. Climate at a Glance Divisional Time Series. https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/divisional/time-series/0402/phdi/all/3/1895-2023?base_prd=true&begbaseyear=1901&endbaseyear=2000

NASA, 2023. Atmospheric Rivers

https://ghrc.nsstc.nasa.gov/home/micro-articles/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.

President’s Update – Spring 2023

American Institute of Hydrology

March 15, 2023 

President’s Update

I am truly energized about my new leadership role these next few years with AIH. As President, I want to make connections, provide synergy, and fully utilize the strong leadership qualities of our Board members and members at large. I am excited about our committees and initiatives – not only for the resulting benefits, but for the process of getting to know each one of you through your involvement. It is critical that all AIH members get involved, whether it’s helping establish the DEI scholarship, expanding our webinar series, or improving our website for AIH members and the public.

Introducing New Board Members!
Salam Murtada, President Elect 2023-2024

Salam brings a wealth of experience to this position from his two-year tenure as Director of Institute Development and one-year as Treasurer. Salam will be transitioning out of his role as Webinar Committee Chair and into the role of President Elect! Salam will be continuing to engage with members and help improve the recertification process.

Luciana Kindl da Cunha, Director of Institute Development

As Director of Institute Development, Luciana will be taking on the role of Chair of the Webinar Committee. We are very excited to see the webinar series continue to expand under the guidance of this important Committee. If you have ideas for upcoming webinars and how to improve webinar outreach, delivery and access, contact Luciana to join the Webinar Committee! Luciana will also be helping the DEI Committee establish and sustain the AIH’s first DEI Scholarship Program.

 

Membership Renewal

If you haven’t yet renewed your AIH membership, do so today!
Renew Membership Here

 Benefits of AIH membership include:

  • Certification as a professional hydrologist or hydrologic technician
  • Membership as a hydrologist-in-training or student member
  • Free access to our webinar series
  • Eligibility for annual awards
  • Peer and employer recognitions of professional competence in hydrology
  • Opportunity to contribute to AIH Committees and articles in the bulletin  
Recertification Process

In addition to membership renewal, AIH members are required to recertify every five years by submitting 60 hours of Professional Development Credits (PDC). Please refer to the information regarding credits, listed in your AIH membership account. And note that AIH webinars count towards accumulating the required PDC credits. Please note that we are currently in the process of streamlining the recertification process in order to make it easier. If you have any questions regarding your ongoing certification status, please contact Kory Adams at kadams@aihydrology.org.

AIH Committees

AIH has a variety of committees and groups you can get involved in, and we are always looking for AIH members to join committees. Contact the Committee Chair/Co-Chair listed below if you’d like to join. Don’t hesitate to renew your membership today, so you can get involved with important committee work! 

Committee

Description

Committee Chair 

Contact

Diversity, Equity and Inclusion (DEI) Committee

Committee formed in January 2022. Currently focusing on establishing a DEI scholarship program.

John Ramirez-Avila and Matt Naftaly, co-chairs

jramirez@cee.msstate.edu

and

mnaftaly@dudek.com

Webinar Committee

Develop, produce and deliver AIH’s Webinar Series

Luciana Cunha, Chair

lcunha@westconsultants.com

Communication Committee

Develop and publish AIH bulletin, social media posts, and webpage improvements.

Brennon Schaefer, Chair

brennon.schaefer@state.mn.us

Board of Registration

Review and evaluate AIH application and recertification packages for education and experience, and make recommendations to the Board of Directors.

Nick Textor, Chair

nick.textor@austin.rr.com

As we know in our daily practice, the profession of hydrology is critical to water management. The prediction, modeling and management of extreme hydrologic events is taking center stage, across the nation and the globe, and our work is more important than ever. Thank you for your continued engagement with the American Institute of Hydrology, and keeping the profession of hydrology elevated through your work!

 

President’s Message – Winter 2023

GreetingAIHPresident Jamil Ibrahims! This is my last President’s Message, and it comes soon after our Board of Directors convened for our AIH Annual Meeting. During the meeting, our Board of Directors reflected on accomplishments and challenges from the past year and established specific strategies and tactics to achieve goals for 2023. I’m delighted about the continued achievements of AIH during my tenure as President, and I’m excited about the next steps for the organization.

While our activities and initiatives have attracted many new members to AIH, we experienced significant challenges over the past year in maintaining our previous members through membership renewals. Many members have retired from the hydrology industry, but others either have not updated their member contact information or simply decided not to renew their membership. Critical priorities for 2023 include continued emphasis on promoting the branding of our AIH certifications, and demonstrating the benefits of certification and membership to our members.

As we wrap up 2022, I’m pleased to report that we are nearly complete with a comprehensive update to our database of examination questions for our AIH certification exams. The process established by our team was successful and the approach may be applied for continued updates to our examination questions database. We convened a team of experts during the fall to develop new examination questions. Updates will be completed prior to our next round of examinations.

AIH held two Water New Year events in Sacramento, California and St. Paul, Minnesota, where members of our AIH Board welcomed the season of maximum soil moisture recharge with current and prospective AIH members. My hope is that we continue this ritual and encourage expansion across other geographies.

We also continued to engage with the American Water Resources Association (AWRA) and other affiliate organizations to promote PH certification for hydrologists and HT certification for hydrologic technicians. After a two-year hiatus from in-person attendance, we actively participated in the AWRA 2022 Annual Conference. Our involvement in the conference is detailed in a summary provided by AIH Director for Institute Development, Salam Murtada, in this Bulletin. Additionally, led by AIH Past-President, Dr. John Nieber, AIH collaborated with AWRA to produce a special issue of the AWRA publication Water Resources IMPACT, titled “Hot Topics in Hydrology.” This special issue features articles by AIH members on a handful of current topics and on recent advances in hydrology research and professional practice. We will look to share information on how AIH members can access this great publication at a later point.

We had a wonderful year – and the next will surely be awesome under the leadership of Julé Rizzardo. Look for continued initiatives by our Board to connect our AIH community and advance AIH through promoting the benefits of certification.

Lastly, I will close through reiterating important points you have seen before:

  • A call to all AIH certified members, as ambassadors of AIH, to take pride and flaunt your AIH acronym. Be HIT-, HT-, and PH-proud.
  • Member participation is vital to AIH’s success. We are eager to engage more members in AIH activities. Please reach out to our Secretary/Membership Liaison, Jolyne Lea, at membership@aihydrology.org, to get involved.

Best wishes for a safe, healthy, and joyful 2023.

Sincerely,

Jamil S. Ibrahim PH, PMP, ENV SP

AIH President, 2021-2022

President’s Message – Fall 2022

AIHPresident Jamil IbrahimThis is an overdue update to our AIH members and community about what your AIH leadership team has been up to this year. I am thrilled to announce completion of critical and timely updates to the governing documents for our organization – our AIH Articles of Incorporation (formerly, Constitution) and AIH Bylaws. We initiated the review and update process in 2016. Over the past six years, past and current AIH leadership team members devoted many, many hours to completing a comprehensive review and developing suggested revisions to these documents. This review and update provided a great opportunity to reflect on how we have operated and how we will function in the future. In the spirit of these changes, Leonardo Da Vinci once remarked (translated to English): “When you put your hand in a flowing stream, you touch the last that has gone before and the first of what is still to come.” It is extremely gratifying to see the results of our review/update process in our new governing documents, and I look forward to the next steps.

There are many other great updates to share:

·        Diversity, Equity, and Inclusion (DEI) Committee – Our DEI Committee developed and prioritized a list of initiatives and solicited feedback/input on implementation through a virtual meeting held in March of 2022. Please reach out to Julé Rizzardo (President-Elect) to join the DEI Committee and learn about these great initiatives.

·        Annual Meeting – Our leadership team held our (delayed) Annual Meeting virtually during March 2022. The meeting was supposed to be held during December 2021, to set our trajectory for 2022, but was delayed due to COVD concerns. In addition to specific tactics associated with strategies and goals that were identified by the Executive Director and members of our Board of Directors, we established three “working groups” to address: (1) Technical Journal/Conference Collaboration; (2) promotions, swag, and marketing; and (3) coordination with affiliate organizations. Contact myself or our management office to learn more and get involved. We are scheduled to get back on track and hold our Annual Meeting in December of 2022 (hopefully, in-person) and set plans for 2023.

·        AIH Webinars – Continued our AIH webinars with great presentations by AIH members Richard Koehler (PhD, PH) and Andrew Cohen( PhD, PH).

·        Engagement with Affiliate Organizations – Continued our engagement with other organizations through promoting PH certification for hydrologists and HT certification for hydrologic technicians at the 2022 World Environmental & Water Resources Congress (EWRI); Frontiers in Hydrology Meeting co-sponsored by the American Geophysical Union (AGU) and CUAHSI (Consortium of Universities for the Advancement of Hydrologic Science, Inc.); and 11th International Symposium on Managed Aquifer Recharge (ISMAR).

·        AIH 2022 Awards – We Issued our distinguished AIH awards to our 2022 award winners: Bruce Wilson, PhD (Ray K. Linsley Award for Surface Water); Todd Halihan, PhD (Charles V. Theis Award for Groundwater); and Vijay P. Singh, PhD, PH (Robert G. Wetzel Award for Water Quality). Note, we will present these awards to our award winners this year at the American Water Resources Association (AWRA) 2022 Annual Conference during their Awards Luncheon on November 9, 2022, in Seattle, Washington.

·        Examination Questions Database Update – We have a plan in place and are about to embark on a comprehensive update to our database of examination questions for our AIH certification exams. Updates will be completed prior to our next round of examinations, scheduled for November 2022.

As I’ve stated in each of my messages previously, member participation is vital to AIH’s success. We are eager to engage more members in AIH activities. Please reach out to our Secretary/Membership Liaison, Jolyne Lea, at membership@aihydrology.org, to get involved.

Sincerely,

Jamil S. Ibrahim PH, PMP, ENV SP
AIH President, 2021-2022

AIH President’s Message

Your AIH leadership team and member volunteers are working hard on exciting initiatives for AIH. Thank you to all who have stepped forward to take on roles to help advance the mission of AIH. We rely on our members’ participation, and we are eager to engage more members in AIH activities. Even if not interested in taking on a leadership role for AIH or getting involved in various subcommittees or groups, we request all our members to be ambassadors for AIH and its certified members. Please contact me or others on our leadership team to get involved.

We are approaching an important pivot point for the focus of AIH’s leadership team. Much energy has been dedicated to improving fundamental processes for AIH over the past few years. While we continue our work to address challenges, changes are underway that we are confident will improve our processes. Examples include rollout of new online member application and database system, and upcoming solicitation for examination support services. Concurrently, we are advancing initiatives related to member engagement, along with collaboration and engagement with other organizations (e.g., American Water Resources Association (AWRA); Consortium of Universities for the Advancement of Hydrologic Science, Inc. (CUAHSI); etc.).

Noted in my previous message, we established a new Diversity, Equity, and Inclusion (DEI) Committee along with a new Webinars Subcommittee. Kudos to: Ed Baquerizo, PH; Megan Gehrke, PH; Ramanitharan Kandiah, PH; Amesha Morris, Matt Naftaly, PH; John Ramirez Avila, PH; and Michelle Woolfolk, PH, and along with AIH leadership team members (Sarah Erck, CMP; Salam Murtada, PH; and Julé Rizzardo, PH) for stepping up to lead AIH’s DEI initiatives. Our Webinars Subcommittee members include member volunteer, Mike Talbot, HIT, and AIH leadership team members (Sarah Erck; Yige Gao, PH; Salam Murtada, PH; and Brennon Schaefer, PH). We’re excited for the rollout of actions from these two groups over the next few months.

On a matter related to inclusion, our Executive Committee (EC) advanced an action earlier this year to eliminate the constraint of nominations for serving on AIH’s EC to only certified Professional Hydrologists (PH)–all certified members (PHs, Hydrologists-in-Training (HITs), and Hydrologic Technicians (HTs) may be nominated to serve for positions on the EC. Subsequently, Chance Fulk, HT III, was appointed as Treasurer, the first HT to serve on AIH’s EC.

Please look for upcoming announcements regarding membership engagement. We’re planning a virtual “meet and greet” event during September and, if all goes well, an in-person social event in Sacramento, California to ring in the New Water Year on September 30. I’m very excited for these events!

 

PS: Note deliberate effort to include AIH certified members’ acronyms with names. I’m calling on all AIH certified members, as ambassadors of AIH, to take pride and flaunt your AIH acronym. Be HIT-, HT-, and PH-proud!

Sincerely,

Jamil S. Ibrahim PH, PMP, ENV SP
AIH President, 2021-2022

AIH President’s Message

The past few months have been very productive for the American Institute of Hydrology (AIH) and we have a lot to be proud of. Since my last President’s message, AIH:

  • Welcomed Chance Fulk, HT III as our new Treasurer–and first HT to hold a position on the AIH Executive Committee (EC). Chance takes over for Salam Murtada who vacated the Treasurer position after election as AIH’s Vice President for Institute Development.
  • Transitioned Salam Murtada from role as AIH’s Treasure to Vice President for Institute Development.
  • Held our AIH 2021 Annual EC Meeting over the week of March 14 to 21, 2021. EC members reflected on 2020 accomplishments/challenges, and proposed actions/initiatives associated to goals and strategies for 2021.
  • Established AIH’s Diversity, Equity, and Inclusion (DEI) Task Force, which will be composed of AIH member volunteers, our AIH Executive Director (Sarah Erck), President-Elect (Julé Rizzardo), and me. The DEI Task Force’s kickoff meeting is scheduled Wednesday, May 19, 2021. If interested in joining the DEI Task Force, contact our AIH management office. Stay tuned for more information on DEI Task Force initiatives/activities in the coming months.
  • Implemented membership application and database changes and a complete website redesign. We’re very excited for these changes to improve ease of application development by perspective members, application review and processing by our Board of Registration, and provide enhanced member benefits through access of information and content. A welcome email with access information to this new certification platform will be going out soon.

My goal is for AIH to be the premier certifying organization and “home” for hydrologists and hydrologic technicians across the United States. The above updates help address priorities shared earlier this year to achieve this goal– and we have plenty of items on our to-do list to further address those priorities, along with the goals and objectives established by each of our EC members. We have a great team and I look forward to reporting on our accomplishments to you again soon.

Please do not hesitate to contact me, Sarah, our management office, or either of our EC members if there is anything you need or if you have suggestions– we are here to serve you!

JAMIL S. IBRAHIM
AIH President

President’s Message

I am thrilled to address our members in my first message as President of the American Institute of Hydrology (AIH). While the new calendar year does not bring the much-needed renewal that I, and I am sure most of you, thirst for – we do have a lot to be excited and enthusiastic about for AIH in 2021. We have a fantastic leadership and management team, along with strong priorities and ambitious initiatives for advancement of AIH. As AIH President, my priorities include:

  • Address “fundamentals” for improved effectiveness and efficiency of association
  • Improve outreach and engagement with AIH members, hydrology community, and public
  • Grow recognition of AIH and increase membership

Over the next few months, I will post messages that delve into more detail for each of these priorities and share status of the many initiatives that our all-volunteer Executive Committee and additional volunteers are working on. In the meantime, I encourage you to either reach out to me directly or contact our management office if interested in taking on a volunteer role to address either of the above priorities and/or AIH’s goal and mission.

Additionally, as I write this message on Martin Luther King Jr Day of Service, I’d like to remind our members to consider what we should do to help our communities advance social justice, racial equity, and inclusion related to hydrology and water resources.
 
In collaboration with Sarah Erck, our Executive Director, our management team, and Executive Committee, we are looking forward to next steps for advancing AIH’s goals and mission. If there is anything you need, please do not hesitate to contact me, Sarah, our management office, or either of our EC members – we are here to serve you!
 
Cheers.

– Jamil S. Ibrahim