The Extended University of Washington West-wide Hydrological Seasonal Forecast System: Covering Mexican Territory

1
The Extended University of Washington West-wide
Hydrological Seasonal Forecast System Covering
Mexican Territory 1Chunmei Zhu, 1Francisco
Munoz-Arriola, 1Adrew Wood, 2Ana Wagner-Gomez,
2Rene Lobato-Sanchez and 1Dennis P. Lettenmaier
1) Department of Civil and Environmental
Engineering, University of Washington, Seattle,
WA, 98195 2) Instituto Mexicano de Tecnología del
Agua, Jiutepec, Morelos, Mexico
Large fluctuations in precipitation streamflow
are common in Imuris and Ixpalino, This
variability is also observed in
evapotranspiration. Precipitation begins to
accumulate relatively early in the year, which
explains the relatively homogeneous
hydroclimatological regime. However, a high
dispersion in the evapotranspiration and
precipitation ensemble members may reflect poor
skill of the ESP forecast in these basins due to
the incidence of winter precipitation and
corresponding high hydrologic variability. In
the Ixpalino basin, on the other hand, the
dispersion of the hydrological ensembles is
greatest during the summer. We are also
evaluating the method in the Oviachic sub basin
of the Rio Yaqui basin. This basin is highly
significant to the agricultural productivity of
northwestern Mexico. This area is located in a
semiarid domain and is strongly influenced by the
North American Monsoon System. In this basin, the
largest dispersion in the ensemble members occurs
during the summer and late winter. One target of
our work is to understand the skill of the
hydrological forecast as the monsoon season is
approaching. We are also evaluating, through
linkage between the forecasts and a water
management model, the impacts of the forecasts
for water resources management.
ABSTRACT
METHODS
Hydrologic forecasting in areas constrained by
the availability of hydrometeorological records
is a notable challenge in water resource
management. Techniques from the University of
Washington West-wide Seasonal Hydrologic Forecast
system (www.hydro.washington.edu/forecast/westwide
) for generating daily nowcasts in areas with
sparse and time-varying station coverage are
being extended from the western U.S. into Mexico.
The primary forecasting approach consists of a
nowcast system that utilizes gridded station data
provided by Servicio Meteorológico Nacional
(SMN), with a fallback option that uses NCEP
weather forecast model nowcast fields (NDAS).
Seasonal forecasts will be based on the NWS
ensemble streamflow prediction method (ESP
essentially resampling of climatology) and on
NCEP Coupled Forecast System (CFS) outputs.
These in turn are being used to force the
Variable Infiltration Capacity (VIC) macroscale
hydrology model to produce streamflow ensembles.
One-year lead time streamflow forecasts at
monthly time step are being produced at a set of
major river locations in Mexico. A case study is
utilizing the streamflow forecasts, along with
forecasts of reservoir evaporation, as input to
the Simulation-Optimization (SIMOP) model of the
Rio Yaqui system, one of the major agricultural
production centers of Mexico. This is the first
step in an eventual planned water management
implementation over all of Mexico.
Hydrological Forecast Operation

• The forecast system produces seasonal forecasts
  twice monthly using the Ensemble Streamflow
  Prediction (ESP) method applied to the Variable
  Infiltration Capacity (VIC) macroscale hydrology
  model. Forty streamflow ensemble members
  represent forecast scenarios for different
  stations located over 15 basins in Mexico. ESP
  ensembles are produced by VIC forced
  climatological data from 1960 to 1999. Key
  aspects of the implementation include
• The initial hydrologic state (at forecast time)
  is provided by the VIC nowcast.
• The nowcast operates by retrieving precipitation
  and temperature data from more than 800
  meteorological stations over Mexico (provided by
  the Servicio Meteorologico Nacional). When the
  station data are not available, we substitute
  NCEP NDAS and/or NARR data.
• Streamflow and fluxes outputs are post-processed
  (as percentiles and means) and are provided as
  numeric data and plot formats that (will be)
  available on the web.

Extended Domain
The UW-West-wide Hydrological Forecast System
produces hydrological nowcasts for the Western US
and Mexico and is being expanded (in
collaboration with Princeton University) to cover
the Eastern US. as well Over the western U.S.
portion of the domain, streamflow forecasts are
made monthly (twice monthly in winter) at about
200 forecast points. The inclusion of Mexico will
expand the forecast domain into Mexico, including
watersheds characterized by the intensive use of
water and lack of hydrological information. The
extended domain includes 14 small basins
characterized by relatively low natural
streamflow, as well as one macro basin in which
streamflow is intensively use for agricultural
practices.
Ongoing work SIMOP and the Rio Yaqui Hydraulic
System

• As part of a project intended to evaluate the
  potential for improving water resources
  management in Mexico through use of climate
  forecasts, we are implementing an operational
  reservoir model in the Rio Yaqui river basin. The
  Simulator-Optimizer (SIMOP) was developed by the
  Instituto Mexicano de Tecnologia del Agua (IMTA)
  to create better predictions of water releases by
  the water storages. Key features of the model
  include
• Use of a genetic algorithm to optimize the water
  used for irrigation in a 1-year cycle using the
  maximum and minimum levels of different dams and
  runoff.  Variables of the genetic algorithm
  include levels and slopes of the change between
  maximum and minimum reservoir levels.
• The model accounts for the water uses in the
  basin (irrigation and potable) through the
  volumes of water available for certain activities
  at each dam.
•  Every reservoir is linked in the file called
  "definition of policies" which are the parameters
  that define the operation of the dam.
• The hydrological forecast system will provide the
  variables needed for its operation, such as
  runoff and Evaporation.

RESULTS and DISCUSSION
Streamflow Forecast
Forecast points within Mexico encompass different
hydroclimatic regions, and water management
considerations. In our initial evaluation, we
evaluate parts of the implementation in three
basins (Imuris, Ixpalino, and Las Perlas). For
example, Imuris is located in an area that has
frequently been affected by multiyear drought
events, which have substantially impacted the
regions agriculture. On the other hand Las
Perlas is located in southwestern Mexico, where
anomalously high and continuous precipitation
events produced flood ad land slides in the
states of Chiapas and Tabasco in October of this
year. Finally, Ixpalino is located the semiarid
central part of Mexico at an altitude similar to
Imuris but with an annual precipitation is
intermediate between Imuris Las Perlas.
CONCLUSIONS
This project represents a first attempt to
implement a seasonal hydrological forecast system
over Mexico. Climatic and hydrological
conditions contrast sharply with those in the
western U.S., the location of most previous
implementations of the ESP method. Hydrological
forecasting over much of the domain is a
challenge due to the highly variable
precipitation regimes, and the extent to which
hydrologic forecast skill can be achieved under
these conditions is a research question that our
implementation is expected to address.
REFERENCES Wood, A.W. and D.P. Lettenmaier,
2006 A testbed for new seasonal hydrologic
forecasting approaches in the western U.S.,
Bulletin of the American Meteorological Society,
87(12), 1699-1712, doi10.1175/BAMS-87-12-1699 Zhu
C.M. and D.P. Lettenmaier, 2007Long-term
climate and derived surface hydrology and energy
flux data for Mexico,1925-2004, Journal of
Climate, 20, 1936-1946. . Note See the author
for other references.