Agent Based Modeling and GIS for Community Resource Management: Acequia-based Agriculture Sarah Wise & Andrew Crooks Department of Computational Social Science swise5@gmu.edu & acrooks2@gmu.edu
What are Acequias? • Traditional system of water management in northern New Mexico • Coupled socio-physical system of ditches and ditch maintenance • Committee of water right holders with precise legal conventions for passing on water versus land rights
Purpose of the Model • Interim goal: to study the viability of acequia- based agriculture with regard to variations in: – population pressure – short-term climate – cultural valuation • Ultimate goal: to support policy work which requires an understanding of the importance and impact of acequias
Study Area: Taos, New Mexico • Population: 5,062 • Acreage - 1,444,480 acres in county – 50.0% Federally controlled – 6.7% State-owned – 4.3% Native American land – 38.2% Privately owned • Acequias built by 1696, town of Taos formally settled in 1725 All information from Taos County Chamber of Commerce
Source: Google Maps
Source: Google Maps
Source: Google Maps
Source: Google Maps
Data 1. Acequia location and ownership 6. Slope/elevation 2. Land use 7. Hydrological system 3. Location of urban centers 8. Population demographics 4. Roads Resolution • Spatial: a raster space measured at 30m sq • Temporal: one tick per year, for 100 ticks
Real-world spatial, Corresponding modeling temporal, methodologies implemented and behavioral processes represented Cultivation and sale of crops Linear programming Real estate market Agent-based model Hydrological system Network Acequia participation Agent-based model (maintenance of ditches, use of water, etc.)
Crop Model If cropland is adjacent to an acequia which experiences at least some minimum waterflow, crops will grow. Income = Crop price * Parcel size
Hydrological Model • Rainfall – Fed by a uniform application of rainfall across the environment once a tick • Propagation – Water flows downhill until it reaches a hydrological feature, and then along the given (elevation-derived) network. Water flows through the acequia network depending on the permeability of the links • Sedimentation – Every year, acequias experience sedimentation and their permeability decreases slightly. This process is reversed by the Parciantes’ annual cleaning efforts
Real Estate Model • Real estate agents pick random Parciantes and formulate their bids according to the following properties of the chosen Parciante’s land: – Constraint = Budget – Transport Cost – Utility = Amenity α * Distance β – Offer = Constraint * Utility 2 /(weight 2 + Utility 2 ) • Approach taken from Filatova et al’s (2009) model of land markets
Acequia Participation Model • Every tick, each Parciante agent must pay to maintain its acequia rights. The cost is proportional to how many rights the agent has, the length of acequia to maintain, and the number of other Parciantes helping them. Cost = Weight * Rights num * Acequia length / Acequia members • Parciante agents have different cultural valuations of their participation in the acequia system.
Interactions between different kinds of agents
Verification • The model was built as part of an iterative process, so that each component was tested as it was developed • Example: – The water network
Verification • The model was built as part of an iterative process, so that each component was tested as it was developed • Example: – The water network
Sensitivity Test 1.Measured – Conversion of Agricultural land to Urban – Change in number of Parciantes – Change in number of functioning Acequias 2.Found – All parameters had the expected impact on the measured variables
Results • Comparison of three scenarios: 1.Traditionalists with low costs 2.Prodigal Sons with high costs 3.Followers with medium costs • Constant rainfall, demand profile, and physical profile
Traditionalists
Traditionalists
Traditionalists
Traditionalists
Prodigal Sons
Prodigal Sons
Prodigal Sons
Prodigal Sons
Followers
Followers
Followers
Conclusions • The acequia system is sensitive to variations in cultural valuation among its members • Changing the cost of acequia maintenance has a significant impact on how tenable farming is as a lifestyle • Weather, population pressure in the form of demand for land, and crop prices influence the system overall
Thank you! Comments, questions, suggestions? Emails: swise5@gmu.edu Web: css.gmu.edu acrooks2@gmu.edu socialcomplexity.gmu.edu gisagents.blogspot.com
Acknowledgements • The authors would like to acknowledge of the Department of Computational Social Science and the Center for Social Complexity at George Mason for providing support for this research. • We are deeply grateful to Michael Cox for sharing his data on the Taos, New Mexico acequia system with us. • This work is inspired by the research of John Paul Gonzales of the Santa Fe Institute, who is himself an acequia parciante.
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