>> Laura: LAST WEEK, THE RIO GRANDE WITHIN THE ALBUQUERQUE REACH STARTED TO DRY.

ON MONDAY, THERE WERE FIVE MILES DRY IN THE CITY, 12 MILES DRY NEAR LOS LUNAS AND 32 IN THE SOCORRO AREA.

UPSTREAM, RAINS, STILL REWET THE RIVER HERE AND THERE BUT THIS DRYING WILL KEEP HAPPENING THROUGHOUT THE SUMMER AND THE FALL.

THE STATE OF THE RIO GRANDE IS SOMETHING WE HAVE LONG COVERED.

THE RIVER IN SOUTHERN NEW MEXICO IS DRY MUCH OF THE YEAR.

AND MORE SUMMERS THAN NOT IN THE PAST 20, THE MIDDLE RIO GRANDE HAS DRIED DOWNSTREAM OF ALBUQUERQUE.

BUT THIS YEAR, THIS IS THE FIRST TIME IN DECADES THAT THE ALBUQUERQUE STRETCH HAS TURNED TO SAND.

IT IS BY NO MEANS UNEXPECTED.

THOUGH THE SIGHT OF THAT EMPTY CHANNEL IS SHOCKING TO ALL OF US.

IN THE PAST, WHEN THE RIVER DRIED IN ALBUQUERQUE, THAT IS BECAUSE ALL THE WATER COULD BE DIVERTED FOR IRRIGATION, FOR EXAMPLE.

BUT THERE WAS STILL WATER UPSTREAM STORED IN RESERVOIRS ON THE CHAMA RIVER, A TRIBUTARY OF THE RIO GRANDE.

TODAY, THOSE SAME RESERVOIRS, HERON LAKE IS STANDING AT ONLY 17% FULL.

EL VADO, WHICH IS UNDER CONSTRUCTION, IS AT 2% FULL.

ABIQUIU, 51%.

I LOOKED BACK AT THE DATA AND THOSE THREE RESERVOIRS ARE CURRENTLY HOLDING A QUARTER OF WHAT THEY DID IN 1983, THE LAST TIME THE RIVER IS SAID TO HAVE DRIED IN THE ALBUQUERQUE STRETCH.

MEANWHILE, DOWNSTREAM, ELEPHANT BUTTE RESERVOIR, THE LARGEST IN OUR STATE, IS AT 4% CAPACITY.

CABALLO RESERVOIR 9%.

THERE ARE MANY REASONS FOR THE DRYING.

AND MUCH OF THE RIVER IS STILL DIVERTED FOR IRRIGATION, FOR EXAMPLE.

BUT THE SIMPLEST WAY TO EXPLAIN THE DRYING IS THE RIO GRANDE HAS TOO MANY DEMANDS PLACED UPON IT ESPECIALLY NOW IN OUR WARMER CLIMATE.

WE'LL KEEP COVERING NEW MEXICO'S RIVERS.

THIS WEEK, I TALK WITH UNIVERSITY OF NEW MEXICO PROFESSOR EMERITUS CLIFF DAHM.

HE HAS BEEN STUDYING DESERT RIVERS FOR DECADES AND HE EXPLAINS WHAT RIVER DRYING MEANS FOR DIFFERENT SPECIES THAT CALL THE RIVER AND ITS ECOSYSTEM HOME.

WELCOME BACK TO THE SHOW PROFESSOR DAHM.

>> Dahm: THANK YOU.

>> Laura: A FEW YEARS AGO WE WERE OUT IN THE SANDIAS WITH YOU TALKING ABOUT INTERMITTENT AND EPHEMERAL WATERWAYS.

TODAY WE ARE TALKING ABOUT A PERENNIAL RIVER, THE RIO GRANDE, THAT HAS DRIED.

AS WE ARE TALKING RIGHT NOW, THE RIO GRANDE HAS DRIED FOR SOME SIGNIFICANT STRETCHES IN THE ALBUQUERQUE REACH, NEAR SOCORRO AND ALSO NEAR LOS LUNAS.

I WANTED TO TALK TO YOU.

YOU ARE AN EXPERT IN THIS FIELD, YOU KNOW, ANYONE CAN SEE THE OBVIOUS FACTS AS THE RIVER DRIES, IMPACTS THE FISH, FOR EXAMPLE.

FISH NEED WATER TO SURVIVE.

WHAT ARE SOME OF THE OTHER WAYS IN WHICH A DRYING RIVER AFFECTS DIFFERENT SPECIES OR THE ECOSYSTEM AS A WHOLE?

>> Dahm: LET ME START BY MAKING ONE POINT THAT I THINK IS IMPORTANT AS BACKGROUND AND THAT IS INTERMITTENT RIVERS THAT ONLY FLOW PART OF THE TIME ARE PREVALENT WORLDWIDE.

THERE ARE MORE RIVERS MILES WORLDWIDE THAT ARE INTERMITTENT THAN ARE PERENNIAL.

WE HAPPEN TO LIVE IN NEW MEXICO AND THE ONE RIVER THAT IS SO DEAR AND NEAR TO SO MANY HEARTS IS THE RIO GRANDE AND WE THINK OF THE RIO GRANDE FLOW BEING THROUGH ALBUQUERQUE AS BEING A PERENNIAL REACH.

IT HAS DIED BEFORE SO IT DOES ON OCCASION HAVE INTERMITTENCE.

THAT INTERMITTENCE IS GOING TO HAVE EFFECTS ON BIOTIC COMMUNITIES THAT ARE THERE.

YOU MENTIONED THE FISH, BUT IN ADDITION, THE RIPARIAN FOREST THAT IS THERE IS DEPENDENT ON HAVING A WATER TABLE THAT IS USUALLY WITHIN 10 FEET OF THE SURFACE.

IF THE WATER TABLE STARTS TO DROP FROM THIS DRYING WE MIGHT SEE SOME DEGRADATION PARTICULARLY OF WILLOWS AND COTTONWOODS.

THAT IS ANOTHER GROUP VULNERABLE TO THE DRYING.

YOU ALSO HAVE TO REMEMBER THAT THE DRYING IS IN THE RIVERBED AND THERE IS WATER IN THE DITCHES, THERE IS WATER IN THE CONVEYANCE CHANNELS, THERE IS WATER IN RETURN FLOWS.

SO THERE IS WATER IN THE SYSTEM SO THAT MAY KEEP THE WATER TABLE HIGH ENOUGH THAT WE WILL NOT HAVE PROBLEMS WITH THE RIPARIAN FOREST BUT WE SHOULD KEEP AN EYE ON THEM FOR SURE.

MANY OF THE MORE MOBILE SPECIES ON A REACH LIKE THIS DRY WILL PROBABLY MOVE TO NEW TERRITORY.

OTHERS MIGHT HAVE ADAPTATIONS TO IT.

FOR EXAMPLE, LAYING EGGS THAT WILL BE RESISTANT TO THE DRY PHASE AND WILL THEN HATCH AGAIN WHEN THE WET PHASE COMES.

SO, I THINK THE ONE THING WE SHOULD BE VERY COGNIZANT OF IS THAT THERE ARE SMALL HABITATS THAT ARE RESIDUAL DURING THE DRYING EVENTS.

THE DRYING EVENTS ARE USUALLY FAIRLY PREDICTABLE.

THEY GO FROM VERY LOW FLOW TO LOTS OF PUDDLES AND POOLS TO ACTUAL TOTAL DRYNESS AND IN THAT TRANSITION IT GIVES SOME OF THE ORGANISMS TIME TO COME UP WITH A STRATEGY TO GET READY TO BASICALLY BE SUCCESSFUL OVER THESE DRY STRETCHES.

ONE THING THAT I WILL ALWAYS TELL PEOPLE IS THAT RIVERS ARE RESILIENT.

THEY ARE SOME OF THE MOST RESILIENT ECOSYSTEMS IN THE WORLD.

I EXPERIENCED THAT WHEN MT.

ST. HELENS ERUPTED AND THAT CAME BACK MUCH FASTER.

SO IF WE GET WATER BACK IN THE SYSTEM, YOU'LL SEE RAPID RECOVERY, BUT RIGHT NOW IT IS PRETTY NERVE RACKING TO WATCH A RIVER THAT FOR 40 YEARS HAS FLOWED THROUGH THE ALBUQUERQUE REACH NOW GO DRY.

>> Laura: WHAT ABOUT SOME OF THE SMALLER ANIMALS, YOU KNOW, WHETHER THAT IS INSECTS OR AMPHIBIANS AND HOW THEY KIND OF ALL RELATE TO ONE ANOTHER AND DO WE SEE CHANGES IN WATER QUALITY, THINGS LIKE THAT?

>> Dahm: A LOT OF THESE ORGANISMS THAT ARE MAYBE LESS MOBILE OFTEN WILL LOOK FOR REFUGIA AND THAT IS ONE OF THE THINGS THAT I THINK IS IMPORTANT THAT WE DURING THE DRYING PHASE IS THAT WE SHOULD MAP POTENTIAL REFUGIA WITHIN THE REACHES.

ARE THERE OXBOW LAKES?

ARE THERE WETLANDS?

ARE THERE AREAS WHERE GROUNDWATER STILL IS PERCOLATING THROUGH AND PRODUCING SMALL RIVERS IN THE ACTIVE STREAM.

THOSE ARE THE PLACES WHERE THESE ORGANISMS WILL GO.

SOME OF THE SMALLER ORGANISMS, CERTAINLY SOME OF THE AQUATIC INSECTS AND PLANKTON, THEY LAY EGGS THAT ARE PRETTY RESISTANT TO DRYING AND THEY WILL HATCH BACK UP WHEN THEY ARE REWET.

THERE ARE STRATEGIES THAT MANY ORGANISMS HAVE.

BIRDS PROBABLY MOVED ON TO PLACES WHERE THEY HAVE BETTER HABITAT.

CERTAINLY THE FISH, THOSE THAT ARE BEING STRANDED THAT ARE A CONCERN ARE ACTUALLY BEING CAPTURED AND MOVED.

>> Laura: WHAT HAPPENS WHEN A RIVER SYSTEM DRIES AND REWETS, DRIES AND REWETS?

IS THAT A DIFFERENT KIND OF IMPACT THAN WHEN IT JUST STAYS DRY FOR A LONG PERIOD OF TIME?

>> Dahm: DEFINITELY.

INTERMITTENT RIVERS WORLDWIDE ARE QUITE NUMEROUS AND IN TERMS OF RIVER MILES THERE HAS BEEN A COUPLE PAPERS OF LATE THAT BASICALLY POINTS OUT THERE ARE MORE MILES OF INTERMITTENT RIVERS WORLDWIDE THAN THERE IS IN PERENNIAL RIVERS WORLDWIDE.

SO, THIS IS NOT AN UNCOMMON OCCURRENCE.

I WAS LUCKY ENOUGH TO BE PART OF A GROUP THAT BASICALLY HAD SCIENTISTS FROM AUSTRALIA AND FROM EUROPE AND FROM SOUTH AMERICA AND THESE KIND OF SYSTEMS OCCUR WORLDWIDE.

AND IN NEW MEXICO ABOUT 95% OF OUR RIVERS ARE INTERMITTENT.

AND, SO, IT IS THE 5% THAT ARE PERENNIAL THAT WE OFTEN FOCUS UPON, BUT THE FACT THAT THEY GO DRY AND THEY WET UP AND GO DRY AND WET UP IS SOMETHING THAT BIOLOGIC COMMUNITIES CAN ADAPT TO.

THE QUESTION IS, HOW OFTEN IS THIS GOING TO HAPPEN?

IF THIS IS JUST SOMETHING THAT HAPPENS EPISODICALLY, PROBABLY THEY ADAPT WELL.

IF THIS IS GOING TO BE A LONG-TERM NEW NORMAL THEN LIKELY MORE CHANGES WILL BE NOTICED.

>> Laura: AS YOU'RE LOOKING WORLDWIDE AT SYSTEMS THAT ARE EITHER INTERMITTENT, THAT IS JUST HOW THEY WERE NATURALLY, OR A SYSTEM LIKE THE RIO GRANDE THAT MAYBE IS BECOMING MORE INTERMITTENT, WHAT ARE SOME OF THE IMPACTS THAT WE REALLY NEED TO ANTICIPATE AND BE THINKING ABOUT?

I MEAN, WATER RESOURCES ARE SUCH A KEY CONCERN RIGHT NOW.

>> Dahm: AND SO LIMITED ALSO.

THERE ARE A LOT OF PLACES WHERE THIS KIND OF INTERMITTENCY HAS BEEN STUDIED AND THE AUSTRALIANS PROBABLY LEAD THE WAY BECAUSE THEY HAVE A CONTINENT THAT IS OVERWHELMINGLY SERIOUSLY DRY.

THESE WETTING AND DRYING EVENTS HELP THE ORGANISMS THAT HAVE LEARNED HOW TO ADAPT AND IT IS ACTUALLY SOMETHING THAT BECOMES PREDICTABLE IN THEIR LIFE.

HAVING 40 YEARS WITHOUT FLOW IN THE ALBUQUERQUE REACH, IT WILL BE INTERESTING TO SEE WHICH ORGANISMS CAN FEND OFF THE DRY SPELL VERSUS THOSE THAT HAVE A SUBSTANTIAL REDUCTION IN THEIR POPULATIONS.

LIKE I SAY, SOME OF THE SENTINELS THAT I WOULD LOOK AT ARE THE RIPARIAN TREE SPECIES.

ARE WE GOING TO SEE WILLOW AND COTTONWOOD DIE BACK AND SEE REPLACEMENT BY THINGS LIKE INVASIVE SPECIES LIKE SIBERIAN ELM AND SALT CEDAR.

THAT WOULD BE ONE THING CERTAINLY TO LOOK AT AND THEN OTHER AQUATIC INSECTS AND FISH SPECIES WILL BE VERY IMPORTANT AS PART OF THE ANALYSIS.

>> Laura: WE TALK ABOUT NONHUMAN SPECIES ADAPT.

I AM CURIOUS WHAT YOU THINK ABOUT HOW HUMAN SPECIES MIGHT NEED TO ADAPT TO TO THIS SORT OF WARMER/DRYER CLIMATE IN NEW MEXICO?

>> Dahm: ONE OF THE THINGS THAT WE SHOULD START OUT POINTING OUT IS THAT THIS DRYING THAT IS OCCURRING IN THE RIO GRANDE, IT IS HAPPENING ALL OVER THE WORLD.

THIS IS A BYPRODUCT OF A WARMER EARTH AND THIS IS A BYPRODUCT OF HEATWAVES AND THIS IS A BYPRODUCT OF HUMAN NEEDS FOR WATER COMPETING WITH ECOSYSTEMS NEED FOR WATER.

SO, THIS IS HAPPENING ALL OVER THE WORLD AND THE FACT THAT IT HAS HAPPENED HERE IN OUR HOMETOWN IS SOMETHING THAT GALVANIZES PEOPLES' INTEREST AND HOPEFULLY WILL ALSO ALLOW US TO BEGIN THE DIALOGUE.

IT IS A DIFFICULT DIALOGUE OF HOW DO WE UTILIZE OUR PRECIOUS WATER RESOURCES.

>> Laura: THANK YOU, PROFESSOR DAHM, FOR JOINING ME.

I APPRECIATE IT.

>> Dahm: YOU ARE VERY WELCOME.