Rangeland Rehabilitation: Stabilizing Arroyos

Arroyos in the desert southwest are major conduits of water across the landscape and during the rainy seasons can be major sources of erosion on a lightly vegetated landscape.  On the 756 acres of the Painted Pony Resort just several arroyos contribute to the majority of erosional damage on the estate.  These arroyos collect water from the west flanks of the Peloncillo mountains which is concentrated into 3 arroyos by bridges along the old El Paso and Southwestern Railroad running along the base of the mountains.  The water collected on the up slope side of the railroad bed is funneled through the bridges and across the property down these 3 arroyos eventually reaching the San Simon Riverbed.  The concentrated and rapidly flowing water erodes both down through the soils and also moves the arroyos laterally.  The high velocity water makes roads on the east side of the estate impassible and washes out culverts and crossings which require significant repair work.  While the changes in drainage patterns as a result of the railroad bridges is beyond one persons ability to easily change, the arroyos resulting from a century of landscape modification can be managed to reduce the damage caused by concentrated high velocity water.  

One of several arroyo management techniques in use requires stabilization of the arroyo banks.  Over 10' deep in places on the estate, arroyo banks frequently collapse and stabilization would reduce the amount of soil eroded during the rains.  But what sort of stabilization technique is applicable?  Being in favor of utilizing low cost materials that are available on the landscape this is the approach most frequently chosen.  Many times people toss in whatever garbage is available into arroyos to slow water flow and protect the banks, but this approach results in an arroyo strewn with leftover wood and metal products which randomly catch sediment and is unsightly (the out of sight out of mind approach).  An alternative approach is to utilize plants for stabilization.  In this case, a native species of ground spreading gourd Cucurbita sp.. 

Members of this genus are low growing ground covering annuals and perennials, in many species the fruit is edible and include cultivars of squash and pumpkin.  Adapted to arid climates and growing well in sandy soils they can be found along roadsides and the gourds may be collected in the late summer.  Producing about 300 seeds/gourd, 3 species of Cucurbita are found on the estate, Cucurbita digitata , Cucurbita foetidissima, and an unidentified species.  The green developing gourds turn yellow when dried and are easily spotted on the landscape for collection.  Arroyo stabilization requires harvesting the gourds and extracting the seeds which are then planted high along the edges of arroyos.  The gourd produces a taproot allowing it anchor itself deeply in soil ensuring it will not wash out with periodic high water and hold the soil.  The long vines it produces cover the ground, absorbing energy and slowing water, and will hang along vertical surfaces allowing its large leaves to protect the underlying soil, reducing soil loss.

Previous tests with planted Cucurbita along the entrance driveway resulted in plant coverage over areas of barren ground which has allowed additional grass to establish itself.  So this is being expanded to treat problem arroyos on the estate.  Collected seeds were planted at about 50 locations along a segments of 2 deep arroyos at the bottom to the top at a depth of 1-2".  Starting at the old bridge, quarter sections of gourds were cut and planted along the banks for a distance of several hundred feet.  Next years crop of gourds should spread downstream with the goal of creating more plants that will stabilize these problem arroyos.

Fruit from C. digitata, C. foetidissima, and an unknown species harvested from the estate.

Looking downstream along a problem arroyo, treated by planting native gourds .

Looking upstream at an old El Paso and Southwestern railroad bridge that funnels water creating problem arroyos.

Native Cucurbita along an arroyo showing how the vines and leaves provide cover for developing grasses.