SAHRA frames its science and stakeholder activities
in a river basin context. Basin-focused science
yields a synergy of activities that helps to drive
science integration and, because stakeholder issues
are tied to river basins, also helps to drive the
application of research results. SAHRA’s
primary geographical focus is on two river basins
(Figure 1): the Rio Grande/Rio Bravo and the Upper
San Pedro, although we maintain interest and some
activity in the Salt-Verde and Rio Conchos basins.
Three stakeholder-relevant integrating questions
(Table 1) is being used to further focus SAHRA scientific
research in these two river basins. All of these
questions are or will soon become critical for the
wise management of water resources in semiarid and
arid regions and can be addressed only by researchers
operating in center mode through the consistent deployment
of integrated, multidisciplinary science. The three
questions, which are broad-based and capable of engendering
and crosscutting many related topics of inquiry,
touch on scenarios that are of prime interest in
this region: land use changes, population growth,
and climate variability.
RIPARIAN
QUESTION: What are the costs and benefits of riparian
restoration and preservation?
In the semiarid Southwest, most
human settlements, irrigated agriculture, and regional
biodiversity are located in riparian corridors. These
riparian systems integrate the hydrologic and biogeochemical
processes that occur within a basin. Consequently,
water resource management decisions may impact river
systems not only through changes in streamflow, but
also through changes in water quality, the socioeconomic
value of the river system, and the structure and
diversity of the riparian ecosystem. A complete evaluation
of the costs and benefits of important management
decisions regarding riparian preservation and restoration
therefore requires an integrated, multidisciplinary
understanding. SAHRA research consequently focuses
on developing fundamental, process-level understanding
in three areas: 1) determining the water balance
of riparian systems, 2) evaluating ecosystem dynamics
and values, and 3) understanding nutrient and solute
sources and cycling. The resulting understanding
will further the development of integrated river
system models that stakeholders can use to evaluate
costs and benefits of potential restoration or preservation
efforts.
WATER MARKETS QUESTION: Under
what conditions are water markets and water banking
feasible?
In the Southwest, water markets
and water banking are increasingly viewed as potentially
effective mechanisms for allocating water resources,
providing economic benefits and avoiding potential
conflicts associated with water scarcity. For these
mechanisms to be truly effective, detailed knowledge
of the available water supply and the factors that
affect water demand is critical. To this end, SAHRA
is developing products to better estimate precipitation
rates and snow-pack volumes at the basin scale. SAHRA
is also improving understanding of the factors that
determine residential, industrial, and agricultural
demand for water, using approaches such as experimental
economics and water use micro-logging to disaggregate
demand. These products and knowledge will then be
integrated into a model that allows water resource
managers to consider the trading of water rights
and third party impacts in evaluating the potential
of market-based mechanisms to allocate water resources
effectively.
VEGETATION QUESTION: What are
the impacts of vegetation change on the basin-scale
water balance?
Vegetation change is a common
feature of the Southwestern landscape. Over the last
several decades this has occurred in the form of
shrub invasion of grasslands, expansion of pinyon-juniper,
thickening of ponderosa pine forests, and anthropogenic
land-use changes. More recently drought related fires
and bark beetle infestations are resulting in large-scale
vegetation change. While a widespread perception
exists that such changes have reduced water resources
available for human use, research that documents
the actual changes on the basin-scale water balance
is lacking. SAHRA seeks to understand the role of
vegetation type and structure in the partitioning
of rain and snow into evaporation/sublimation, runoff,
and infiltration, and how moisture stored in the
soil is shared between transpiration, recharge, and
streamflow. SAHRA’s approach involves: 1) intensive
field measurements at selected plot- to hillslope-scale
sites to investigate vegetation controls on partitioning
and guide development of methods to model and scale
these processes; 2) exploring the use of remotely
sensed data to determine key hydrologic variables
across basins; and 3) integrated modeling to evaluate
the effects of vegetation change.
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