3.6 Simulation protocol of GH-LUDAS
3.6.2 Time-loop procedure
assigning each value to its respective household agent. After the creation of the set of these 200 agents, the population will be augmented by creating copies of these basic agents until the actual population size is reached. These new agents are allocated to the same village as their original, and distributed within the different compounds in the respective village. The actual population sizes for each of the villages were calculated from statistical data sets provided by the Ghanaian Survey Department.
In the third step, when all agents have been created, the distances of these agents to landscape features such as main river and dams are calculated. Furthermore, if dams have been inserted into the landscape, the distance to dams are updated for all landscape agents.
Finally, since virtual household agents should also own patches as in reality, this procedure allocates land holdings to each of the agents. The sizes of these land holdings are given by the holding variables of the agents, as called by the first procedure. The location of these patches is given by the land-allocation procedure, which works as a loop. In each loop, each agent is allowed to select one single patch, and the procedure will be run until all agents are assigned their specific amount of land.
The loop itself runs as follows: As long as patches within the Landscape Vision are still available (i.e. Powner=’nobody’), the called agent will mark a random patch within this vision as his. If no patch within the Landscape Vision is available, the agent will select a random patch within the same village, and if none of these are available, the agent will select a random patch from the whole catchment. The design of this procedure avoids a biased pat-tern of distances of owned patches to their respective owners.
main steps of this time-loop procedure are outlined in the following:
Delete Household Agents
Create New Household Agents
Allocate Credit
Decision to do Irrigation
Choice of Irrigation Method
Labor Allocation
Static Phase of Cultivation
Moving Phase of Cultivation
Calculate Yield
Calculate Income
End of Dry Season?
Categorize Agents
Update Household Variables
Update Patch Variables
Calculate Statistics
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Figure 3.10: Time-loop procedure
1. Update of age and deletion of household agents. In this step, the age of the household agent is updated, and if the maximum age is arrived, the agent is deleted.
2. Creation of new household agents. This procedure creates new household agents ac-cording to the new population size, as calculated by the parameters of population growth, and the number of deleted agents without successor..
3. Allocation of credit. According to the annual credit access rate, agents are selected randomly to obtain credit, whils those agents are preferred that had obtained a lesser number of credits do far.
4. Decision to do irrigation. In this step, each household agent generally decides between doing irrigation and not doing it. This procedure is dependent on both the household’s
state and the biophysical attributes of the landscape (see section 3.4.1; procedure Dirr).
5. Choice of irrigation method. If the decision to do irrigation is positive, the agent will decide here about the irrigation method he is going to use (see section 3.4.1; procedure Dmethod)
6. Labor allocation for the dry season. In this step, the dry-season labor pool will be allocated to the various production lines, dependent on the group the agent belongs to.
Furthermore, for each credit the agent had obtained, a shift in the labor allocation is executed.
7. Static phase of dry-season cultivation. Here, the agent starts cultivating his own irri-gable patches, by deciding about land-use type and input of fertilizer and labor. The procedure runs as long as the required labor and cash resources are available.
8. Moving phase of dry-season cultivation. In this step, the agent will start searching for new patches, but with the same land-use related decisions as in the static phase. The procedure runs until the combined labor and cash resources are exhausted, or until all irrigable patches within the Landscape Vision of the agent are under use.
9. Calculation of dry-season yield. This procedure calculates the yield of each irrigated plot in the local currency, using productivity functions (see section 3.3.1).
10. Calculation of dry-season income. In this step, the cash and gross incomes for each production line are calculated. Furthermore, the gross income is augmented according to the credit access of the household and the credit deflating factor.
11. Labor allocation for the rainy season. Similar to the dry season, the rainy-season labor pool will be allocated to the various production lines, being dependent on both the agent group and the credit access patterns of the household.
12. Static phase of rainy-season cultivation. Here, the agent starts cultivating his own patches, by deciding about land-use type, management, and input of labor. The proce-dure runs as long as the required labor resources are available.
13. Moving phase of rainy-season cultivation. This procedure is similar to the static phase, apart from the fact that the agent now shifts to new patches, if labor is still available.
Once the agent has borrowed a patch from another agent, he will try to continue using it in the next time step.
14. The calculation of rainy-season yield. This procedure calculates the yield of each cul-tivated plot in the local currency, using productivity functions (see Chapter 5).
15. The calculation of rainy-season income. Equivalent to the rainy season, in this step the cash and gross incomes for each production line are calculated, also being dependent on the credit access pattern of the household.
16. Agent Categorizer. After the season-specific procedures have terminated, the agent cat-egorizer will allocate each agent to its nearest group, while the values of the grouping criteria for each group are updated according to the mean criteria values of the group members.
17. Update of household variables. According to the group the agent has been assigned to, the group-specific household variables will be updated. Furthermore, all other house-hold variables that are the result of the previous procedures will be updated for the next time step.
18. Update of landscape variables. This routine, called the land-cover transformation pro-cedure, will update the cover type for those patches that had undergone a land-cover change during the simulation of the previous procedures.
19. Statistical calculations. Finally, statistical parameters will be generated for both the landscape and the population. On the population side, mean annual income as well as the corresponding Gini Index are calculated, and on the landscape side, land-cover and land-use fractions are calculated for both seasons.
4 LAND-USE DECISIONS BY HETEROGENEOUS HOUSEHOLD AGENTS