Observations of the Main Vernal Pools on the Mesa de Colorado in 1997 - 1998

Introduction to this page.

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.)

1997 December 17: I was surprised to find that the two small pools by the road had water in them, and even more surprised to find that the large pool had no water in it! Last year all three pools filled up at the same time.

There is no trace now at all of the burn from last spring. Ranger Rob Hicks told me that the first serious rain of the season just washed all the black away.

Another 15' or so of boardwalk has been added at each end, removing the necessity of placing a temporary ramp when the water level is high. Crushed gravel has been placed on the entire path from the Vernal Pool Trailhead to the main Vernal Pool.

There are some green patches within the area of the main pool that look like grass. The large clumps are starting to green up. The dried-up cracked algae mats can still be seen on the bottom of the pool area.

The rocks within the pool area look like they have desert varnish on top, but normal colors where the water from the pool covers them at high water.

1998 January 5: Still no water in big pool. Smaller ones still have some water, but it looks like less than previous observation.

1998 January 12: The last rain did it! The big pool has begun to fill, and the two smaller pools look a bit fuller than before. There were about 30 geese honking away as I approached.

The little hoppy creatures are back again, which may be springtails. They are about 1 mm long and can hop about 1" = 25 mm. Their density is about 15 per square foot on average. A little stream of water comes into the pool from the north and forms a little pool next to the boardwalk. In that pool, there are probably thousands of them all jammed together.

The pond covers the large clumps and so the greening of them can no longer be easily observed.

1998 January 19: Pool a bit deeper than last week. A cloud of 10-20 gnats accompanied me from the vernal pool trailhead to the lip of the pool, but remained behind as I descended gently to the pool. On the way back I ran into vast clouds of them in the same area blown into my face by the wind.

About 20 geese honked and flew away as I approached the big pool.

The number of springtails is down, only about 5 per square foot on average. With the sun out, I noticed that although they look black on the side of the boardwalk, they are white on their underneath, which must be exposed when they hop.

I saw exactly two fairy shrimp swimming away, so they are just beginning to appear.

1998 February 2: There are four flowers blooming now:

There was only one small swarm of gnats on my hike in and one at the pool. Much more noticeable was the vandalized sign near the pool, which was removed later that day. Some idiots had tried to burn the plastic coating of the sign, leaving large black ugly marks. Fortunately, insurance will replace the sign. I had previously recorded some of the text that was on the sign.

The springtails are nearly completely gone now - I saw only a few. Little red shrimp are now the most numerous creature, with 15-20 per surface square foot of water. Fairy shrimp are next, with 5-6 per square foot, followed by the little gray shrimp at 3-4 per square foot.

1998 February 9: When I stopped my car at the vernal pool trailhead, it was enveloped with what looked suspiciously like a cloud of hundreds of mosquitos. I decided not to get out of my car, but drove down the road, turned around and parked in a different spot! It was still gnat city walking to the pool, with so many back at the car that I didn't change my boots sitting on the back of my car, I just dived in!

The pea gravel path was half gone in many places, especially as one descended to the main pool, replaced by a flowing stream that had cut a little channel into the path.

The pool was higher than I had seen it at any time in the last two years. The water was very muddy, so I couldn't get a count on the density of creatures. It looks like the red shrimp are larger by a factor of 2, but this was hard to tell. Very rough numbers might be about 10 red shrimp per square foot, 30 gray shrimp, and ~1 fairy shrimp.

The springtails were back, and there were other things in the water. Mosquito larvae were numerous.

1998 February 21: No gnats or mosquitos! Or maybe they were just dispersed over the group of ~20 Fallbrook Boy Scouts (Desert Pacific Council Pack #735 Den #5) and their parents who invited me along on their hike...

The wildflowers now alone justify a trip to the area. Just north of the main pool are hundreds of shooting stars, the wild ancestor of florist's cyclamen, creating large purple fields of flowers. Another large clump is found just west of the adobes along the main ranch road. The small yellow daisies are much more numerous and create large yellow fields of flowers.

The pool depth has decreased since two weeks ago, even though we have had a lot more rain since then. I don't think wind pushing the water level higher for the previous observation can account for it, but we'll see from subsequent measurements.

Trails other than the vernal pool trail now have signs posted recommending against travel on them due to muddy, sloppy, slippery conditions, which is definitely true. We slogged through the trail from the main vernal pool to the adobes, and the trans-preserve trail from the ranch road to the vernal pool trail.

A few springtails are still around. The little red shrimp are now very numerous with 30-50 per surface square foot of water. Fairy shrimp are next, with ~10 per square foot, followed by the little gray shrimp at 3-4 per square foot.

1998 March 1: The decrease in pool depth is real! In spite of a lot more rain, somehow, someway, the pool has continued to fall at a regular rate. Furthermore, the pool is falling at the same rate as it did last year after it stopped raining last year.

Something must be using up the water - perhaps it is the plants that are starting to stick out of the water everywhere, and especially the plants sticking out of the water at the edges. This assumes the conventional wisdom is correct about the clay sealing the bottom of the pool, and thus that very little seeps into groundwater.

The plateau is quite stunning now - there are carpets of pretty flowers. The yellow carpets are still vibrant with color, and are now joined by carpets of deep purple shooting stars and of wonderful-smelling light purple ground pinks. In addition, there are numerous blue dicks, yellow violas, a tall yellow buttercup with a waxy flower, and a few california poppies. Now is a great time to go see the Plateau! Apparently, a lot of other people think so, too, since the parking at the trailhead was completely filled up with a steady stream of people.

The Reserve has done some great trail work on the vernal pool trail. A ditch has been dug alongside the trail and waterbars on the trail to divert the water and sandbags have been lined up alongside a very wet section of trail. It looks like more pea gravel has been added as well.

A watersnake greeted my arrival at the pool. The little red shrimp continue to be the most numerous species with 30-50 per surface square foot of water. Some of them were mating. Fairy shrimp are next, with ~5 per square foot, followed by the little gray shrimp at 3 per square foot in one spot, but about 30 per square foot at another spot. Algae have really taken off and cover the underwater plants. A dragonfly followed me about as I surveyed the pool. There are even some springtails clustered at corners of the boardwalk.

1998 March 16: The poppies are in full bloom now, popcorn flowers (Plagiobothrys undulatum) and shooting stars are now blooming along the vernal pool trail. It's cloudy this morning (and will drizzle later for most of day) and thus most of the flowers are not open.

A portable potty is at the vernal pool trailhead now, verifying that large numbers of people are visiting.

Signs of the end of the blooming are beginning to appear. Filaree or Clocks (Erodium cicutarium) (References 1; and 2) is showing its interesting seed pods that look like vertical spikes or swords.

Vandals have hit the plateau again - several posts of the boardwalk have been lifted up and rocks placed underneath, giving it a very warped nature. Please be alert for signs of such vandals and try to get their license plate.

The pool is also in its final stage, very different from 2 weeks ago. Algae mats cover 10-30% of its surface, and a good deal of the underwater plants. Grasses have blades a foot above the pool's surface.

Very few fairy shrimp are seen. There are about 10 springtails per square foot, 40 red shrimp, some with an egg sac at their rear, 5 gray shrimp. There are ~1-2 tadpoles per square foot and ~1-2 "worms" on the surface.

1998 March 18: The two small pools look like they are nearly gone due to the grasses hiding the surface. The small yellow "buttercups" looks like they are nearly finished blooming, but that may be only due to the time of day (5:30 pm).

Algea mats cover ~80% of the surface of the large pool. I saw a single owl's clover near the trailhead.

1998 March 23: Owl's clover now much more abundant. Four new flowers are in bloom - a member of the mallow family with robust flower stalks coming out of a robust plant, with flowers at nodes along the spike; a small bright purple flower with 5 petals; a miniature (flower) version of the popcorn flower; and an iris with a blue small flower with 6 petals.

Goldfields (Lasthenia chrysostoma), the little yellow flowers among the first to bloom, are now definitely nearly finished. The fields of yellow are now a much larger plant with waxy petals.

The green spike rush and algae mats now make the pools look like the water is gone in many parts, even though the water is still there. In particular, from a distance the boardwalk looks like it goes through a meadow, not a pool!

The pool depth continues to decline at a steady rate.

1998 March 30: Although the flowers are definitely past their peak, the pools have been rejuvenated from the recent rain. From a distance, the boardwalk at the big pool no longer looks like it is surrounded by meadow, and the two small pools are clearly pools again. The algae mats cover only 50% of the surface now of the big pool, and grasses are about 1' above the surface.

The pinks, popcorn flower and shooting stars are nearly gone, but there are still some patches of goldfields holding out. The tall buttercups are about half done. But the owl's clover is at its peak now.

There are about 50 springtails per square foot of pool surface, 5-10 red shrimp, 5 gray shrimp and about 1 tadpole. The tadpoles are definitely fatter now.

1998 April 22: The pools have continued their depth decrease. The closer of the two small pools to the vernal pool trailhead again looks from a distance like it is a green meadow - the farther pool still has visible water. The pool still shows visible water, but nearly 90% of its surface is now covered by algae mats.

There is almost no life in the pool now. Not of trace of shrimp, only a few springtails, 1-2 aquatic bugs and a few water snakes.

Much to my surprise, there are still many flowers, even though the appearance is very different. Most of the Plateau is dominated by tall grass in seed, and thus the patches of color previously seen from a distance are no longer visible. However, up close, there are still stunning collections of wildflowers. Owl's Clover and the small lupine are at their peak now, and there are still patches of goldfields, blue dicks, ground pinks, california poppies, cranebill, mustard and popcorn flowers. There are even some patches of color due to checker mallow.

There is not a trace of a "ring of flowers" appearing around the pools.

1998 April 27: I had the good fortune to meet Gordon House, who identified some of the flowers I hadn't known: the checkered mallow, the California buttercup and the Mariposa Lily. He told me that both the tall white flower and short white flower were known as popcorn flowers. Gordon publishes a list every month of the flowers in bloom, which I will try to get and put on the web.

Gordon pointed out a Mariposa Lily and said that this was the first bloom of the season.

The main pool has the tiny white popcorn flowers blooming, but you cannot see the white from a distance.

1998 May 8: One of the two small pools is all green from a distance, and the other is 80% green. The main pool is 90% green from a distance. Up close, the algae mats are much less noticeable because they are somewhat under the pool's surface, probably due to the last rain putting a lot of clear water in the pool. The pool seems lifeless except for one water snake.

Lots of Mariposa Lilies and owl's clover are blooming now. The checkered mallow is blooming at the ends of its flower stalks.

The edge of the main pool has lots of small popcorn flowers, and the flower resembling a johnny-jump-up that has 3 purple wide petals, two more narrow petals and a yellow center. The north end has lots of the 5 petal purple flowers.

1998 May 28: Fields of purple color have appeared again, thanks to the Mariposa Lilies! There are tons of them still in full bloom. The Santa Rosa Plateau continues to amaze me this year with new flowers taking over after previous flowers have faded away. There is a new shiny purple, 3' tall 4-petal flower blooming now. Fields of mustard now create yellow patches. Larkspur blooms here and there. California poppies and the small lupine flowers still are blooming.

The owl's clover, blue dick and checkered mallow are ending, and only a few tall popcorn flowers are around. I saw one patch of ground pinks still.

There are many dragonflies now, which are "herded" in front of me as I walk, confined to the pathway by the tall stalks of grass, which are usually waist-high. Perhaps 20-30 dragonflies are in front of me as I walk.

The two small pools are all green now from a distance, as is the main pool, despite its still being quite full thanks to the continuing rain. The main pool was gone last year in early May. This year, in late May it is deeper than it was in early March last year! But still no life in it. Having water in the pool this late is clearly too infrequent for any visible life form to take advantage of it.

Although there is no ring of color around the main pool from a distance, up close there is a noticeable ring of small popcorn flowers and johnny-jump-up look-alike that creates white and purple patches. The jump-up twin is blooming even in the deepest part of the pool, sticking up out of the top of the pool's surface. The tall stalks of grass look gray-purplish from a distance, adding another contrast.

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Copyright © 1997-2000 by Tom Chester.
Permission is freely granted to reproduce any or all of this page as long as credit is given to me at this source:
Comments and feedback: Tom Chester
Updated 30 May 1998 (Typo corrected 15 July 2000; broken links removed 1 November 2000).