Hydrological drought sensitivity to land use changes in a Northwestern Mexico River Basin Francisco Munoz-Arriola1 Chunmei Zhu1, Andrea Ray2 and Dennis P. Lettenmaier2

1. Department of Civil and Environmental Engineering, Box 352700, University of Washington, Seattle, WA 981952. NOAA Earth System Research Laboratory, 325 Broadway, Boulder, CA 80303-3328

Regional Climate Forum for Northwest Mexico and the Southwestern U. S. , Ensenada, Baja California, México April 10–11, 2008

ABSTRACTLand-use changes can strongly affect streamflow generation. In most cases, deforestation and agricultural intensification increase streamflow while afforestation reduces it. In semi-arid basins, such as the Yaqui River basin (YRB) in Northwestern Mexico, changes in streamflow generation may impact the sustainability of the region's agricultural practices. Water resources in the YRB are influenced by different climate-phenomena, such as the North American Monsoon, El Niño Southern Oscillation (ENSO), and the Pacific Decadal Oscillation (PDO), and by anthropogenic activities. Here we evaluate the sensitivity of drought events in the YRB to land use changes under different climatological conditions. Periods were identified where the ENSO and the PDO influence the temporal variability of streamflow from 1949 to 1999, using wavelet analysis. The drought events, which were influenced by these oscillations, were identified using runoff-percentile anomalies. Increments of the agricultural and afforestation practices were implemented as boundary conditions, and used by the Variable Infiltration Capacity model (VIC) to simulate the hydrological surface components of the YRB. Droughts during the non-monsoon months of La Niña and the warm phase of the PDO years were sensitive to increase in crop land-use in the northernmost part of the YRB. The rest of the basin observed an increase in runoff, which reduced the drought occurrence. Drought sensitivity to afforestation was higher during the monsoon months. In neutral years followed by El Niño and in years during the cold phase of the PDO, drought sensitivity to afforestation was the highest during the monsoon months.

STATEMENT OF PURPOSE: To assess the streamflow drought sensitivity to land use changes under different climatic regimes in the Yaqui river basin

Study Domain

Three sub basins of the Yaqui River basin were evaluated, Angostura and Paso Nacori, considered natural streamflows and Oviachi a streamflow diverted for water storage (hydropower generation and irrigation).

CONCLUDING REMARKS• Intensification in agriculture is reflected in changes in the number of drought days. Munoz-Arriola (2007) observed a reduction in the streamflow produced by increments in the crop surface at Angostura (opposite to what occurred at Oviachi and Paso Nacori). This is reflected in the increment of drought days during the monsoon months. During non-monsoon months the streamflow generation is influenced by events such as snow melting (may be important in Angostura during the spring months) and low evapotranspiration producing a reduction in the drought events and its duration. This shows the importance of land surface processes such ass soil moisture dynamics and consequently the inhibition of evapotranspiration due to availability of water in the first soil layers.

Evaluation of Simulated Streamflow

Drought Analysis

Observed

Simulated (naturalized

Small- mid- (El Niño [EN], La Niña [LN], and neutral [N] years), and large-scale clime conditions (warm and cold PDO)were identified using the squared wavelet coherency (Grinsted et al. 2004) and information in literature, observed in the climatological composites of simulated streamflow (Larkin et al 2004 and Mantua et al 1997). Monsoon months were assumed June, July, August, and September, the rest of the months are non-monsoon months.

VIC Features: Macro-scale and semi-distributed model Subgrid representation of the spatial variability in:

Land surface vegetation classes Soil moisture storage capacity as a spatial

probability function (Xinanjiang Model) Drainage from the lower soil moisture zone (baseflow)

as a non linear recession (ARNO model) Evapotranspiration based on the Penman-Moneith

equation (Mid- and bottom soil layers) The routed runoff transport is linear and time invariantSpatial Resolution: 1/8 o (Zhu and Lettenmaier, 2006)Temporal Resolution: 3-hourly1949 to 1999Temporal ResolutionDrought analysis uses the percentile method with the lower

20% threshold (Andreadis et al 2006)

Calibration: Munoz-Arriola et al. (to be submitted) Climate conditions: (see below) • El Niño Souther Oscillation Index (SOI)• Pacific Decadal Oscillation (PDO)Identification and Evaluation•Wavelet Analysis•Composites (from Larkin et al 2002 and Mantua et al. 1997)

•Under current conditions short draught events (5 days) dominate in all sub-basins•Paso Nacori experiment the highest number of draught events•The largest drought event occurred in Angostura during 1999 (79 days)

Angostura Case• Pre Monsoon

•Drought days were reduced during EN and LN years•During N years draught days increases•Changes in the number of draught days occurred during the warm phase of PDO

•Monsoon•During all climate conditions the number of drought days increases•Increases in the number of drought days were higher during N, followed by LN, and EN with the smallest changes•During the Warm PDO occurred 92% of the changes

•Non-Monsoon•All years experimentd a reduction in the number of drought days•Warm PDO experimented a reduction in the number of days of drought while during cold PDO occurred the opposite

Angostura

Oviachi

Paso Nacori NAMS

Gulf of California

Gulf of California

Sierra Mafre OccidentalPacific Ocean

Sonoran Desert

Gulf of Mexico

Aros-Papigochi River

Moctezuma River

Bavispe River

Yaqui River

Yaqui Valley

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Squared Wavelet CoherenceCross Wavelet Transform

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Sub-basins

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EvNedleaf EvBroadleaf DsNedleafDsBroadleaf Mixed Forest WoodsWooded Grassland Closed Shrubland Open ShrublandGrass Crop Bare

•An increment of 3% in the crop surface produces

• Streamflow decrease in Angostura

•Paso Nacori and Oviachi streamflow increases

• Changes in streamflow are associate to:

•Deficit in soil moisture and the consequent inhibition of evapotranspiration previous to the monsoon and the first stage of monsoon (June-July)

•Soil moisture increment after the monsoon onset favors evapotranspiration

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Pre-Monsoon Monsoon Post-Monsoon

•Streamflow deficit produced by the monsoon droughts is higher than those in the pre-monsoon and post monsoon months.•Post-monsoon droughts are consistently smaller in number of days and events•The strongest drought events and occurred at Angostura during the pre-monsoon months•The largest drought event occurred in Angostura during 1999 (79 days)

pre-monsoon monsoon post-monsooncurrent 3% current 3% current 3%

EN 608 602 345 367 114 112LN 148 139 240 291 45 34N 1066 1081 794 830 332 300

COLD 1277 1277 768 776 309 314WARM 545 545 611 712 182 132

Warm PDO: (1947-1976)Cold PDO: (1977-1995)Pre-Monsoon: (January, February, March, April, May)Monsoon: (June, July, August, and September)Post-Monsoon: (Octuber, November, and December)

Andreadis, K.M. and D.P. Lettenmaier, 2006: Trends in 20th century drought over the continental United States, Geophys. Res. Lett. , 33, L10403, doi:10.1029/2006GL025711 Larkin, N. K., and D. E. Harrison (2002), ENSO warm (El Nino) and cold (La Nina) event life cycles: Ocean surface anomaly patterns, their symmetries, asymmetries, and implications, J. Clim., 15, 1118-1140. MunozArriola, F., D. Lettenmaier, C. Zhu..and R. Avissar. Hydrological Response to Land Use Change in the Yaqui River Basin (submitted, Water Resources Research) Munoz-Arriola, F. (2007). Hydrological Response to Precipitation Discrepancy and Land Use Changes in the Yaqui River Basin. Civil and Environmental Engineering Department, Duke University. Ph. D. degree inCivil and Environmental Engineering.Zhu C.M. and D.P. Lettenmaier, 2007: Long-term climate and derived surface hydrology and energy flux data for Mexico,1925-2004, Journal of Climate, 20, 1936-1946.