Guest commentary written by Robert Shibatani:

Insofar as climate change and water resources is concerned, there are many related issues, but don’t let that lead you astray.  Stay focused on the fundamental water issue tied to climate change.  The whole premise behind climatic change in water resources is that it is changing our global hydrologic baselines.  That’s it.  Simple, straightforward, uncomplicated.  In this short piece, the focus is on water quantity and related quality issues as illustrated through the use of hypothetical examples taken within California geography.  The GHG side of climate change which is more policy-related and not directly linked to water resources is not discussed here. 

So, what does this all mean?  It means that the existing and future water flow regimes, in our rivers, streams, and creeks are slowly but surely shifting as global climates continue to change.  What is meant by shifting?  This refers to the changes in such things as watercourse discharge, peak flow rate, and seasonal timing, essentially, the hydrograph.  In snow dominated regions like California where the traditional spring freshet has always been the major hydrologic event the year, such changes can have significant implications.  In watersheds reliant on snowmelt, the seasonal hydrograph is flattening as snowpacks continue to decline.  Springmelt and high river flows will further decrease and river flows will ultimately more closely match direct rainfall-runoff responses as the timing lag offered by the snowpack gradually diminishes in importance.  

Such changes affect all other facets of the hydrologic regime and thus, water management.  This includes groundwater recharge, flood management, reservoir infill and refill, the scheduling of hydropower generation, sediment/nutrient transport, maintenance of instream flows, water temperature, and the list goes on. 

From this realization, two potential lines of questioning emerge.  The first is whether a proponent is seeking to use historic hydrology as a standardized or representative baseline of what could occur in the future.  In other words, a baseline that does not include any climatic shifting.  And second, what analyses, if any, has the proponent undertaken that takes into consideration climatic forcings capable of influencing the anticipated future hydrologic regime under which the proponent requests a proposed project be approved?  

Here are but a few examples to provide context of where such questions would be relevant. 

        • A project developer seeks to convince the SWRCB that, based on the historical record of the South Fork American River from which it intends to divert additional water, there will be adequate supplies to meet the temporal (seasonally scheduled) demands of a new project.

        • A Norcal water agency wishes to enter into a long-term water transfer/assignment agreement with another water purveyor in the Bay Area and intends to use the historical record of the Feather River watershed as the means to demonstrate sufficiency of supply.
        • A groundwater management district in the Central Valley wants to codify its safe yield with a regulatory agency and intends to use historic annual hydroclimatology to calculate anticipated future recharge rates from annual Sierra Nevada runoff.
        • An irrigation district in the Delta is updating its long-term water master plan and is using the historic annual hydrology of the Delta along with existing SRI and SJI river indices to project future annual delivery allocations that it expects will be available.
        • SMUD wishes to renegotiate some of its power-purchase agreements knowing that the ability to meet existing scheduled demands may be significantly affected by continually shifting inflows to its UARP reservoirs from which it generates power.
        • A water agency operating several dams that have flood control functions, wants to amend its reservoir operating rules which it knows to be outdated, but is not sure of which upper basin hydrological database should be used – a long-term historic database from gauge data – or a new future climate sensitized The former is readily available, while the latter will require additional effort and cost. 

From a water quality perspective, some potential project examples where climate change would be important might include situations where:

        • A wastewater treatment plant that discharges to the Sacramento River wishes to expand its discharge capacity and is using historic hydrology of the river as the basis for amending its permit (which is largely based on flow related dilution factors).

        • NMFS intends to issue a permit requiring a specific instream water temperature threshold for certain times of the year and bases this requirement on an evaluation of the historic hydrology of the river, in one of the upper Sacramento River tributaries for example.

From the above hypothetical examples, it is evident that a proposed new project’s viability depends, in large part, on which hydrologic baseline is used.  Since water-related project approvals are typically based on some increment of change (e.g., the magnitude of which often defines the significance threshold), then the baseline or starting point becomes very important.  For decades, engineers and hydrologists simply used the long-established historic record as the baseline.  They would say, for example, that the long-term average mean monthly flow for the American River at its mouth in February was 5,300 cfs.  They would assume that this long-term historical mean would remain unchanged into the future.  The only future evaluation requirement would be in the context of guessing which future actions (e.g., regulatory, infrastructural, institutional) would be deemed reasonable and feasible under a cumulative impact assessment.  Never was any thought given to the possibility that the actual climate and resulting hydrology would also change.  And of course, there was never any regulatory requirement to do so.

Today, proponents are faced with new challenges.  First, they have to recognize that the future hydrologic baseline is changing, in some cases rapidly.  Second, they have to develop a means of establishing what that future baseline looks like.  Third, they have to try and isolate their own project’s incremental effect to the constantly changing hydrologic baseline, relative to what climate change is doing.  Fourth, they have to pick a future timeframe upon which their climatic forecasting, hence, hydrologic analysis is to be based.  And fifth, they must determine if the waterways and waterbodies potentially affected by their project will be affected in a spatially uniform manner by a shifting climate. 

These are not necessarily easy issues to address.   For example, teasing out the incremental impact of one’s particular project against a moving baseline that, is already responding to inherent natural variability in both space and time, is extremely challenging.  Remember that project proponents are only obligated to mitigate their own incremental exceedance beyond an established significance threshold.  A moving baseline makes doing this much more difficult.  No project proponent wants to mitigate for an effect that is beyond what their project is determined to generate.

In California from roughly 2000-2010, project proponents were just beginning to acknowledge how climate change could affect water resources, but few were actually including it in their analyses.  None of the key water regulators overseeing California operations (e.g., SWRCB, RWQCBs, CDFG, Water Commission, USBR, NOAA/NMFS, USEPA, or the USACE) had implemented mandatory regulatory requirements to assess climate-forced hydrology.  As a result, no one did.  Many projects were approved, permitted, and implemented during this time without any meaningful consideration of future climate change hydrology. One could argue, with some validity, that those past projects (and there were many) considerably underestimated the potential effects of their project given their omission of any climate change influence.  Some of these documents and the management actions that they still support remain in effect to this day. 

Here’s where it gets interesting.  The primary environmental review legislation used in California, CEQA and NEPA are fundamentally ill suited to addressing today’s projects or even yesterday’s projects, particularly when water resources are involved.  Why?  Because the premise has always been that the hydrologic baseline was a constant, both today and into the future.  Existing condition analyses under CEQA for example, become meaningless under that assumption.  Why approve a project that might have less-than-significant effects today, based on a snapshot of today’s river conditions, when those conditions will be different 20-years from now?  The same applies with NEPA.  Why assume a Future No-Action as a null alternative when the hydrological conditions in the future will be notably different?  Once you acknowledge that hydrologic baselines are indeed dynamic, the whole contemporary impact assessment approach becomes notably weakened.

Fortunately, on the climate change hydrology data side, things have progressed, with DWR taking the lead role in developing various climate and hydrologic datasets. These are now publicly available and can be interchanged with one’s own models/sub-models, variables/assumptions, analytical methods, etc.  

So, where do we stand today?  Technically, we know what should be done, how to do it, why, and under what circumstances.  The legal nuances, however, are much more complex.  In California water resources, the added element of climate-forced hydrologic change introduces a new uncertain dimension.  There are unique perspectives from both the plaintiff and defendant points of view, but insofar as hydrologic climate change is concerned, there is only one issue – the hydrologic baseline.  The only difference is whether you are the one compelled to undertake the analysis or, whether you are the one being asked to review and confirm the appropriateness of the project proponent’s analysis.  

An additional element emerges when a regulatory agency is overseeing some element of the project’s approval and has adopted its own climate change hydrology requirement.  In such situations, both plaintiff and defendant might find it in their best interests to engage in the review of this information (either together or separately).  Regulators do not have sole claim on climate change modeling and analytical correctness (and they have been known to be wrong in the past).   At present, no complete sequence of climate change modeling and hydrologic analytical steps have been tested and ruled by the courts.

As noted earlier, DWR has undertaken the bulk of the climate change modeling legwork and made available many helpful resources, including datasets, guidelines, recommended procedures, etc.  It is up to the user and/or reviewer, however, to decide which of the various datasets (e.g., climate, hydrology, water operations) are appropriate, if any, and which model drivers or assumptions they want to ascribe to in their analysis.

Regardless of whether one is a new project proponent, intervenor, regulator or, agent for any of the above, a few examples of the types of queries that would be of relevance to one’s evaluation might include:

        • Was the GCM/RCM model ensemble selected a reasonable choice given the geography, scale, and features of the project?
        • Were the downscaling methods selected appropriate for the scale and particulars of the project?
        • Was the forcing scenario (RCP) suitable or, did it skew the evaluation one way or the other?
        • Was the modeling timestep(s) appropriately integrated between data transition and final modeling output review?
        • Did the analysis accurately capture snow accumulation, maturation, and melt in generating annual runoff?
        • Did the analysis adequately account for the dynamic interaction between groundwater and surface water and their joint roles in generating runoff?
        • Did the analysis appropriately apply operational and environmental regulations at levels projected into the future that can be deemed reasonable or even feasible?
        • Was there adequate discussion and disclosure of the confidence limits an error bands associated with each of the modeling applications and analytical steps?

Whether trying to prove that a proponent or regulatory agency relied on state-of-the-art technical climate change information or that, as a project proponent, the climate change hydrology analysis was sound, knowledge of and answers to these questions and others is necessary.  In its current undefined state, climate change hydrology, in the right legal/hydrological hands, can represent a powerful tool in litigation.  Since, no current legal standards exist in climate change hydrology analysis, it is up to the party to provide the compelling evidence for climate change forcings and related water resources (hydrology).

What does all this mean for water-related projects in California?  A lot.  For any time there are potential effects to a natural or man-made water body, climate change hydrologic analysis is essential.  From a proponent’s perspective, it is difficult in this day and age to try and convince anyone that ignoring climate change on any of the State’s waterbodies or watercourses is appropriate.  Forensic dissection of climate change hydrology can be used as a strong cross-examination tactic to raise substantial doubt in the eyes of the court.    

At present, there is no rigid protocol, either as a proponent or defendant, in the evaluation of climate change in water resource-related projects and actions.  Accordingly, innovation and creativity are the most desired tactics in dealing with this multi-faceted challenge.  The complexities from both the legal and hydrological perspectives require highly versed experts, not only in their own fields, but also in their abilities to integrate their expertise with other disciplines so that an effective tactical stratagem can be developed and presented before the courts.  For California, our current sensitivity and acknowledgment of climate change and its wide-ranging implications can make it a make or break issue in water resource projects.

About the Author: Robert Shibatani is a consulting hydrologist and water industry advisor with over 35-years combined experience in research, environmental analysis, consulting and expert witness litigation across the globe. He is CEO of The SHIBATANI GROUP, Inc. based in Sacramento, California. <robert@theshibatanigroup.com>

Note:  The views expressed in this commentary are the author’s views, and should not be attributed to Maven’s Notebook.

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