Observations of the Main Vernal Pools on the Mesa de Colorado in 1999 - 2000

Plot Of Pool Depth Vs. Time For The Main Vernal Pool
Chronological Observations
Detailed Bloom Observations


This page contains a chronological record of my observations of wildflowers in the entire Reserve and of the Main Vernal Pools on the Mesa de Colorado in 1999-2000. Each record nearly always begins with observations from the Vernal Pool Trailhead directly to the main pool.

See a more complete Introduction to this page.

The wildflowers are much more visible on the Mesa de Colorado this year, since a controlled burn took place south of the Los Santos / Ranch Roads in mid-1999, which removed the 3-4' tall dry vegetation that greatly decreased the visibility of many of the wildflowers in early 1999. However, due to the very short rainfall season, it is not a spectacular year. General bloom observations are listed here. See also Detailed Bloom Observations.

Despite the complete absence of water in the pools in 1998-1999, the types of fauna that showed up in the pool this year were not only unchanged from previous years, but their numbers were much higher in some cases. What amazing creatures these are!

Plot Of Pool Depth Vs. Time For The Main Vernal Pool

The plot below shows the pool depth (green) versus time at the boardwalk, which is at the edge of the pool. Hence the depth at the center of the pool is slightly greater than reported here. The plot also shows the total rainfall (blue) at my house in Fallbrook, 11 miles south.

(Click on graph for bigger and better image.)

Chronological Observations

1999 October 29: Los Santos Trail, Coyote Trail, Trans Preserve Trail. A controlled burn took place earlier this year, although it isn't immediately obvious to the untrained eye. Without familiarity with the 3-4' tall dry vegetation that had remained on the Plateau for a full year since the growth of early 1998, the ground just looks like it has sparse vegetation.

A closer inspection shows that the soil contains soot amidst the growth that occurred after the burn, and quickly reveals charred plant remnants in various places. The lower branches of many of the oaks have dead brown leaves from the fire, contrasting with the green leaves in their upper branches.

This augers well for a good wildflower season, since the patches of different colors should be visible from quite a distance, just as they were two years ago.

With the vegetation largely removed, a glance shows that nearly 100% of the surface is covered by gopher mounds. I marvel that the ground doesn't simply collapse from all the tunnels that must be present underground. Also, with the gophers packed as densely as possible, I imagine the gopher wars that must go on in the spring, as the adolescent gophers leave their parents and try to claim a patch of land for themselves. The mortality must be high in order to preserve the same number of gophers.

At the southeast corner of the intersection of the Los Santos Trail proper and the Road with the same name, the fire has revealed 20-40 bleached large cattle bones from the ranch period of the Santa Rosa Plateau. No small bones are left, only the large bones like rib, thigh and hip bones.

That intersection also clearly reveals the contrast between the unburned area north of the road, full of dry vegetation, and the sparse burned area south of the road. It amazes me that there is any vegetation at all in the burned area, but a few plants can emerge from the ashes, even without further rainfall after the burn. The same thing happened two years ago.

Aficionados of the "walk-through tree" just north of the Trans Preserve Trail intersection with the Vernal Pool Trail will be glad to know that the hulk has once again survived a controlled burn. Ranger Kevin Smith told me that in 1997 he stood by that hulk with buckets of water in order to make sure of its survival, which he undoubtedly did again in 1999.

Bugs were virtually absent, with only one black fly bugging me on the hike.

Only a very few wildflowers were blooming, including a few penstemons, and three flowers I don't know. Two are about 6" tall, one with yellow flowers along its main stem and the other with similar blue-purple flowers. The third is a 1-2' single main stem, with yellow sunflower-family blooms leading to clusters of seeds like small dandelions. A few everlastings were still in their dried "everlasting" phase.

Trip Log for this hike.

2000 February 25: Vernal Pool Trail. After being gone for 19 months, the pools exist again! It was surprising to see the pools today, since only 6.5" of rain has fallen so far in Fallbrook. It took 7.5" in 1997 and 10" in 1998 before the pools appeared, and they never appeared in 1999 despite 8.5" of rain. Of course, the concentration of this rain within only a week or two must have been the trick that did it. The 8.5" in 1999 was spread about as evenly over the rainy season as possible.

Very little life is in the pool. There were abundant tiny spiders crawling all over the edges of the boardwalk, and there were a very small number of the little hoppy creatures, about one per square foot.

2000 March 2: Vernal Pool Trail, Trans Preserve Trail, Coyote Trail, Los Santos Trail. The fairy shrimp are back! After skipping an entire season, living without water for 19 months, the fairy shrimp are back in numbers not seen by me since I have been observing the pool since spring 1997. There are 100-200 baby fairy shrimp in a 1 square foot column of water, a density at least ten times higher than I have seen before. The fairy shrimp are 2-4 mm long (~1/8"), with only a few at 4 mm and most at the smaller end. I could clearly see the larger ones as swimming on their backs, a sure clue to their identification, with their little appendages beating at high speed to propel them.

The fairy shrimp are clearly hard to see unless you know what you are looking for. On the way in, I passed one person who said that there weren't any in the pond! A couple came to the pool while I was lying on my stomach looking at them, and it took them nearly five minutes to observe them even as I was pointing them out and describing their characteristics. On the other hand, Jane Strong picked them out within seconds of my pointing them out. Furthermore, their distribution is far from even in the pool. Most were found on the northwest side of the boardwalk, and even there some parts had zero shrimp.

Here are some tips to help identify them. First, study the picture on the display board with the bench just before the trail descends to the pool. Second, note that the shrimp are nearly transparent, and are shorter than an inch at most, so you'll have to work at seeing them. Third, lie down on your stomach with your face a foot or two from the water. Fourth, check at least four distinct areas near the boardwalk. Fifth, don't let your shadow fall across the part of the pond you are examining. Sixth, have patience!

The tiny spiders on the boardwalk were completely gone, but the rocks projecting above the pond's surface had about one grown spider per rock. No gray or red shrimp were present. There were a handful of dragonflies at the pool, including one pair that did their acrobatic maneuvers while mating! Jane Strong identified some beautiful strings of frog's eggs in the water, looking like fluorescent uniformly-spaced seeds on an ethereal medium.

Poppies and lupines have just started blooming. There was one poppy on the way to the pool, and another poppy in the field below the Trans Preserve Trail. Lupines were blooming on Poppy Hill and sporadically elsewhere. Wild cucumbers were blooming several places, including a stunning specimen on the Coyote Trail. A few mustards and everlasting were sighted in bloom as well.

I looked over my records for 1997 and 1998, and in both years the fairy shrimp could be seen for almost two months, and the red and gray shrimp for almost three months, with eggs appearing near the end of their lifetimes. So the fairy shrimp should be visible through April, and the sight of them carrying their eggs should be seen around mid-April, if past is a guide.

2000 March 9: Vernal Pool Trail, Punta Mesa Trail, Adobe Loop Trail, Trans Preserve Trail. Water, water everywhere! The two smaller pools now have a waterway that either connects them or almost connects them, which I don't recall ever seeing before. There are pools of water everywhere, and most trails seem to have rivulets flowing along them or across them in many places. Where there is no standing water, the trails are all mud, gooey and sticky or slick and slippery. Travel along the trails is now much slower due to the need to step carefully everywhere. I suddenly fully appreciate the pea gravel on the Vernal Pool Trail to the pool!

The main vernal pool is very full, ~14" deep, up from ~6" just a week ago. (The deepest I've measured it was ~16" in 1997.) The fairy shrimp have grown, although there are fewer of them. The shrimp are now 6 - 12 mm in length (~1/4 - 1/2"), up from 2-4 mm last week. I estimate that there are now about 50 per square foot, down by a factor of 2-4 from last week. I suppose "infant mortality" is the normal course of affairs for species that produce many young. There are about 5 water fleas per square foot.

The pool now is a chorus of frogs. I couldn't see any frog's eggs in the pool, probably due to the increased depth of the pool. I saw another one of my old friends, a paramecium-shaped creature ~10? mm in length in the surface tension layer of the water. There was a new creature I don't remember seeing before: a "race car driver" on the surface of the water who zoomed along the surface in straight lines. I didn't get a clear look at him, so can't report anything else about him. I saw no dragonflies today.

There still are few flowers. Two lace parsnip's were blooming near the Vernal Pool Trailhead, a couple of poppies by the Trans Preserve Trailhead, gooseberry along the way to the Adobes, and a single everlasting along the Adobe Loop Trail. The hoary-leaf ceanothus have fat buds on them on the Punta Mesa Trail.

As I was checking out the ceanothus, I heard an unaccustomed sound - water! Although I hadn't planned on continuing on the Punta Mesa Trail, I had to find out if it was true. It was! The De Luz River, which normally has a trickle of water at best, was an actual stream. There was no way to cross it without getting your boots wet.

What a transformation everywhere from the dry conditions of the last two years!

2000 March 19: Vernal Pool Trail, Multiuse Trail north from Visitor Center. This was a Sunday after the Riverside County newspapers had published articles on the pool, and hence the SRP was crawling with people. At 1:30 pm, 35 cars were parked at the VP Trailhead, and the docent said that perhaps 500 people had already been there. At 2:45 when I got back, there were 49 cars parked there.

Although there were people every hundred feet or so on the trail, it wasn't too crowded at the pool, and it was easy to still enjoy and study it. In contrast to 10 days ago, the shrimp were a piece of cake to see since they had grown larger and some of them now had eggs. The shrimp are now 1/2 - 1" long. About 10% of them, including all body lengths, had what appeared to be a single egg sack, with a few of the largest ones have two egg sacks.

The red and gray shrimp (my terms for them, and probably not their true names) are both back, and I saw a couple of tadpoles. While the red shrimp looked as they always have to me, the gray shrimp looked immature.

The densities were harder to estimate, due to the number of people at the pool. I estimated ~100 fairy shrimp per square foot, 50-200 red shrimp and 50-200 gray shrimp, and one tadpole.

The trails had dried out considerably. The pool was lower by 2". Instead of "water everywhere", it looked like post-rainy season conditions everywhere. Plants were bursting into bloom, but usually represented by only a few early bloomers. On the VP trail I saw a number of lace parsnips, a few johnny-jump-ups, a few goldfields, a few poppies and a single buttercup. On the Multiuse Trail I saw numerous locoweeds, hoaryleaf ceanothus, manzanita and Mission manzanita in bloom, and a single purple nightshade blooming.

2000 March 23: Vernal Pool Trail, small portion of Trans-Reserve Trail. The Mesa de Colorado is about to burst into bloom! Enough goldfields are now open so that one can visualize the patches of color that will soon exist. Buds on blue dicks are now common on the Trans-Reserve Trail. The wild cucumber is now just past its peak bloom there. One new plant was blooming, a muilla along the Vernal Pool Trail. Otherwise, I observed the same plants blooming I saw four days ago.

The surfaces of the two small pools now look much-diminished from the trailhead, as if they are covered with algae or plant material, but viewed from the north they still appear full of water. The main pool continues to dry up, now 10.5" deep, down from 14". The surface near the boardwalk is already beginning to accumulate pond scum on its surface.

The major change in pool life is the large number of tadpoles swimming about, up to ~20 per square foot in some areas. For some reason, the tadpoles are mainly concentrated in the shallow water at the west edge of the boardwalk, where there are few fairy shrimp. The bodies of the tadpoles are up to 1/4" long, with no visible features such as legs.

The fairy shrimp seem mostly unchanged from four days ago, still 1/2 - 1" long, about 10% with eggs, with peak densities ~50 per square foot. Red shrimp number about 200 per square foot, and gray shrimp perhaps ~50 per square foot. There are a couple of "paramecium" type worms on the surface per square foot. Matthew, my 9-year-old son, noticed a huge water bug, about 1" long, that looked like some sort of beetle.

I checked the "pothole" filled with water near the Vernal Pool Trailhead, and it looked like there were gray shrimp in it, but I didn't study it close enough to be sure.

Even on a Thursday at ~3 p.m., there were several cars at every parking area in the Reserve.

2000 April 2: Vernal Pool Trail, Trans-Reserve Trail, Hidden Valley Road, Los Santos Trail. One of the two smaller pools near the trailhead now appears to be gone, but the other ones still seems to have plentiful water. The main vernal pool continues to evaporate. It now is ~9" deep, and without more rain will vanish in May.

Since this was Sunday, there were again crowds of people at the Plateau. It was somewhat difficult to make observations along the boardwalk with children running around, poking in the water and trying to capture tadpoles. It's amazing that anything in the world survives children, especially those without parents to tell them not to disturb the plants and animals of the Preserve. I saw one child walking back from the pool whose shirt was half soaked with water.

Nonetheless, the denizens of the pool showed only gradual changes from ten days ago. Surprisingly, the 1" fairy shrimp are now almost entirely gone from the pool, but the ~1/2" shrimp are still numerous, ~20 per square foot at maximum. About 10% have eggs. The red shrimp still number ~200 per square foot at maximum, and I observed some of them mating, performing a crazy curlicue dance very different from the single red shrimps. The gray shrimp number ~10 per square foot. The "paramecium-type" worms are more numerous now at ~5 per square foot. Other people observed the large water beetle, but I didn't see any.

Most people's attention were focused on a water snake a bit over a foot long, and on the tadpoles, which have grown noticeably, ranging from 1/4" to 1/2" now. A few are starting to form frog features.

About 30% of the water surface near the boardwalk is covered with algae.

Jane Strong and I observed 47 different species of flowers in bloom on April 2, compared to 16 as of March 23. The bloom observations are described in detail on a new page devoted to Bloom Observations.

The trails are now bone dry nearly everywhere, a marked change from 23 days ago.

2000 April 14: Vernal Pool Trail, Trans Preserve Trail. The two smaller pools are gone, replaced by carpets of green. There are a few good patches of goldfields to the east of the pool along Avocado Mesa Road.

It was late afternoon on a cool, cloudy day when I visited, which perhaps accounted for the muted appearance of the flowers along the trail. The ground pinks had closed, but they looked much less numerous than in wetter years. Along the trails, there was the usual variety of plants blooming, but the plants were less vigorous, and the patches were sparser than in wetter years. The sense I had on previous hikes of the blooms heading toward a peak was gone, replaced by a realization that maybe this is now the peak. See Bloom Observations for the record.

The pool is only 4-6" deep now, and is just 2-3 weeks away from its projected disappearance in very early May without further rain. Unlike 12 days ago, the pool is very different now. The number of creatures is way down, either their response to sensing some feature that tells them that the pool is soon to vanish, or because the shallow pool is no longer hospitable for them. This is quite different from previous years in which the pool was deeper at this time and thus lasted a month or two longer.

The hoppy creatures have made a reappearance on the surface of the pool, and number in the thousands per square foot of water. There are only ~20 per square foot of red shrimp, ~5 of gray, ~1 tadpole and ~1 3/4" "scooty" bug that I have never seen in the water before. The unknown bug resembles a bee in body shape (roughly rectangular), and swims in spurts. I observed no fairy shrimp at all, which have either all been eaten (by tadpoles?), or reached the end of their lifespan and no further generations could hatch in the pool in its current condition.

No bugs have troubled me in any of my visits to the Plateau, unlike previous years.

2000 April 19: Vernal Pool Trail, Trans Preserve Trail. After the inch of rain in the last two days, there is now a small visible patch of water on one of the two smaller pools. Other than that, the pools are still visibly carpets of green.

The main pool rose only by roughly the amount of rainfall, implying that essentially no runoff made its way into the pool, due to the dry ground. The pool will now disappear in mid-May if no further rain occurs.

My visit again occurred near the end of the day. The plants showed no visible improvement due to the rain, but perhaps that was to be expected due to the short time since the rain.

Life in the pool is declining rapidly. About 80% of the pool's surface is covered with algae, making it difficult to do an accurate census. Although the hoppy creatures still number in the thousands per square foot of water, there are only ~5 per square foot of red shrimp, ~1-2 of gray, ~20 of the paramecium-type worms, and no tadpoles or fairy shrimp.

Short white popcorn flower is now blooming at the outer edge of the pool, which was covered with water only a month ago.

2000 May 4: Vernal Pool Trail, Punta Mesa Trail, Monument Road, Trans Preserve Trail. The two small pools are still visibly carpets of green, with no discernible color from a distance. The main pool is only 4" deep at most, and is so shallow in many places that toads have no problem moving through the pool and keeping their heads above water.

Although there are plenty of blooms, there are very few "patches of color" seen from a distance anywhere. It is clear now that peak bloom on the Plateau occurred in mid-April. Although there are still many blooms to be seen, the grasses are tall with seed and a number of species are no longer blooming. It was not an outstanding year, but it was and is still quite nice.

However, the almost-gone main Vernal Pool has carpets of short popcorn flowers and downingia at its margins, perfuming the air. Peak bloom for the Pool may still be in the future.

The main pool still has numerous hoppy creatures, perhaps 200 per square foot, ~20 small toads, ~1 snail and ~1 water snake. Unlike previous years at this time, the algae mats are not prominent at all, although they do cover nearly all of the patches of water that can be seen. Most of the surface of the pool is taken up with live plants. The grasses are ~2' high in most of the pool, with the former edges covered with flowers.

As in previous years, there are no rings of similarly-colored flowers. The only color visible from a distance is gold which covers perhaps 1/20 of the circumference of the pool. By the boardwalk, white popcorn flowers and downingia dominate, but they are not readily visible past about again 1/20 of the circumference of the pool.

On Monument Road, I observed some curious shapes on the surface of the road at anthills. The shapes resembled subterranean termite tubes. Most were fully enclosed parallel to the road, but some were vertical and cutoff at the road surface, revealing their hollow nature.

2000 May 26: Vernal Pool Trail, Ranch Road, Trans Preserve Trail. Jane Strong noticed that from one's car at the trailhead, the Plateau looks all grasses in seed, with few or no wildflowers. But as soon as one hits the trail, there are wildflowers in abundance! To be sure, the wildflowers are still no match for the show of two years ago. But they are still a delight to observe.

The most common wildflowers today are Clarkia, Mariposa Lily and Brodiaea. Although these flowers are nearly everywhere, peak bloom is clearly past. The blue-eyed grass, mallows, blue dicks and buttercup, the most common wildflowers a month ago, have nearly completely finished blooming.

The exception is at the main Vernal Pool. The water is gone, but replaced with beautiful masses of downingia, scenting the whole pool area of the boardwalk with a pleasant sweet strong fragrance. Peak bloom for the pool is probably occurring now, and may in fact be among the pool's best bloom in recent years due to the lack of dried mats of algae covering a lot of the surface.

Three weeks ago there were only a few patches of downingia. Today, those patches have nearly finished blooming, but there are four large patches seen from a distance, with more visible at the pool. The downingia is accompanied by several patches of gold, which are not goldfields. They come from a much taller flower (~1') with five petals, each with three "fingers" at the end like tidytips.

Although all the other pool residents are long gone, the water snake was still slithering by the boardwalk. What happens to water snakes when the water dries up?

The two small pools have a light green center, ringed with darker green, with no other patches of color visible. The ancient former small pool along the Vernal Pool Trail, halfway from the Trailhead to the Main Pool, is also well marked by the darker green, which is a native grass that is just blooming now.

While we were resting at the Adobes, we noticed a peculiar low density, high-rate-of-speed bee swarm. From a distance, the swarm was very noticeable. But within the swarm, one could hardly notice it since the density was so low. This swarm continued to go by for at least 30 minutes. Since we easily saw about 5 bees go by per second, there had to be at least 9,000 bees total! Amazingly, this is close to the 12,000 bees in an average swarm (which varied from 2400 to 49,000).

The trails had recently been mowed or weed-whacked, making it easier to traverse them. A new bench has been added to the Trans Preserve Trail 0.2 miles north of Hidden Valley Road, allowing one to sit and enjoy the view to the west.

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Copyright © 1999-2003 by Tom Chester.
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Updated 28 January 2003.