DATA AND UNDERSTANDING WZ, 
channel by a simple brush dam, or even by felling a single tree. 
With the water flowing in the bottom of a deep trench, a much 
more elaborate dam is necessary, even to make diversion possible. 
The flood peaks increase because of loss of natural valley storage, 
and for this reason also, any diversion works must be more 
elaborate. 
Not everyone living in an arid region can depend on major 
irrigation projects. To the subsistence homesteader who depends 
mostly on his own axe, plow, cow, and horse to make a living off 
the land, valley trenching, as it occurred in New Mexico, was a 
major calamity. 
For the earth scientist the arroyo problem poses many ques- 
tions, among which are these: (1) Assuming that grazing use has 
contributed materially as a causal factor in arroyo cutting, can a 
change in land use, specifically, a reduction in grazing pressure, 
slow down arroyo growth or perhaps reverse the trend and lead 
to valley aggradation? (2) How much can small structures, water 
spreaders, and other minor works retard gully development? 
(3) What is the future trend of physiographic development in 
these alluvial valleys under present conditions of land use? On 
the answers to these practical questions depend a host of decisions 
which would affect the welfare of many people. 
Practical measures, including gully control, watershed treat- 
ment, and grazing management, have been applied locally in 
various degrees over a period of two decades. Additional data 
have been collected to describe the vegetation, the soils, the 
streamflow, and the sediment yield. Yet it appears that the 
answer to these questions is not much closer than it was in 1933. 
Need for Fundamental Research 
What is lacking is a satisfactory understanding of the hydro- 
logic, physiographic, and biologic mechanisms on which depend 
the stability or instability of the alluvial valley. In the hope of 
achieving practical answers, no provision for long-term research 
in fundamental mechanisms has been made. Although some 
excellent research was started at Mexican Springs in 1933, lack 
of continuity of funds forced a curtailment of those efforts and 
