4.1. Definition of the Model
The methodology adopts a simplified decision model to represent the decision-making process of the case study WA to select the best alternative among a set of actions upon receiving new information. The model assumes that a WA is managing water procurement and supply for a given agricultural region and that the WA must plan some actions in advance during two different inter-correlated decision time steps. The first decision step is supposed to be at the time of seeding/transplanting, far in advance to the irrigating season, and involves the decision (action): release concessions to the minimum/maximum operational capacity of the supply network. Such a decision is conditioned by the WA’s expectation about the state of the world (state, from now on): dry/regular season. The second decision step is supposed to be at the time of supplying water for irrigation and involves the decision: deliver/do not deliver water to irrigation districts. Such a decision is conditioned by the WA’s expectation about the state: need/no need water for irrigation. In chronological order, the first decision influences the second. Thus, the usability of such information is then dependent on the accuracy of the messages provided by the information service in both decision steps and on the stakes in the decisions, contributing to determining the expected consequences of using the information. In the following section, we provide an analytical representation of the decision process, both in case of un-informed decisions and ICT-informed decisions. In the latter case, in each decision time step, a new piece of information is provided by a message.
The decision model described before represents a decision process taking place in conditions of uncertainty. In the first place, we assume that the decision process involves a set of actions,
X, and a set of states,
S. The combination of the possible actions with the possible states determines the associated consequences,
, measured in terms of economic payoff of the decision,
. The subscript
denotes a specific action among the set of possible actions and the subscript
s denotes a specific state among the set of possible states, where
and
. For example, the consequence of not limiting yearly concessions for irrigable areas in a regular season is drought losses, and the associated payoff is the economic estimation of such losses. Thus, the actions taken by the WA have uncertain consequences determined by the probability of occurrence of upcoming states,
. In our case, the probability coincides with the climate-relative frequency of the event. Assuming the WA is acting rationally, it will base the choice of an action on the concept of Expected Value (EV) maximization. The EV of an action depends on the probability of the different states and on the payoff of the set of possible actions under the different states of the world [
21]. With no information service, the maximization of the EV is obtained by the following Equation (1):
In the case of ICT adoption, the WA can receive a message,
, among a set of messages,
M (
). The probability of receiving message
is identified as
, which is measured as the frequency of that message relative to all messages delivered by the ICT. Messages provide information regarding the emerging state of the world. For example, a message can specify that a dry season will occur. Messages might modify the WA’s information environment, altering the expectations associated to the upcoming state of the world. The extent to which the WA reviews this prior expectation follows the Bayes Theorem and is measured by the probability of state occurrence conditional to the message received,
, also known as posterior probability:
where
is the probability of receiving message
, conditional to the emergence of state
, and
is the joint probability of state
s and message
, also known as the hit rate [
18]. This is measured in a likelihood matrix by the frequency of correct messages on all messages delivered by the ICT. As can be noticed, the higher the hit rate of the ICT, the higher the extent to which the WA will revise its prior expectations. This implies that, by means of the accuracy of the ICT, the WA revises its beliefs about a state’s occurrence after receiving a message. This in turn will have an effect on expectations about decision outcomes with direct consequences on the choice of actions, allowing the WA to identify a new optimal action. The EV of this action after receiving a message is determined by the sum of payoffs weighted by the unconditional probability of the message and the respective conditional probability of the states. Considering an ICT delivering multiple messages, the maximization of the EV will be as follows:
Now, consider a simplified version of the model described above, with only two alternative states (
and
), two alternative actions (
and
) and one decision time step. This model can be represented through the diagram in
Figure 4. Payoffs in each state are measured vertically and probability is measured horizontally, ranging from zero to one in a bi-directional segment. Since states are alternative, meaning that one excludes the other, probabilities of state occurrence are complementary (
). Hence, a point along the segment represents both probabilities. In the diagram, the blue line joining
and
is the weighed average of payoffs for action
. This line expresses the EV for that action as a function of probabilities. Similarly, the pink line, which joins
and
, represents the EV of action
. For a given probability, the EV of the optimal action is displayed by the vertical distance from a point in the horizontal segment of probabilities to the higher EV function between
and
. Taking into account an information service that can generate two alternative messages (
and
), either message will lead to a vector of posterior probability,
. The line joining the EV of the optimal action if
is received and if
is received, defines the EV of the message service. This is mathematically represented by the probability weighted average of payoffs. So, following Equation (3), the VOI is graphically represented by the vertical distance from the line of the EV of the message service to the EV of the best un-informed action (green segment in
Figure 4).
Finally, we take into account a decision problem involving decision time steps. Decision steps are identified as sequential decisions occurring during time (i.e., before and during the irrigating season). For each decision step, t, there are independent actions,
, messages,
, and states,
. The set of possible consequences is obtained with the combination of actions and states in each time step, t, for the subsequent combination until the final decision step. In other words, the combination of actions, states and decision steps allows for the identification of the range of final outcomes of the decision process. Since decision steps, states and messages are independent, the expected value maximization problem can be reformulated as it follows:
Hence, during time in the decision process, the final choice of actions made by the WA depends on the accuracy of the messages received until the final decision step. This way, a lack of accuracy in the first messages has a multiplier effect in determining the expected consequences of sub-sequential actions. Finally, in each decision step and for each message received the WA, the WA seeks the optimal choice of actions among those available. This is done through the identification of the optimal informed action (
) achieving the highest EV given the states that can emerge and their relative posterior probabilities. The same happens in un-informed conditions, where, given the prior probabilities of states, the WA identifies the optimal un-informed action in each decision step (
). After optimizing action choices, the VOI can be estimated as the difference between the EV from the sequence of optimal informed actions given the messages received, and the EV of the optimal un-informed actions given the prior information environment:
As can be seen, the VOI of the ICT is positive only when the expected value of the best informed decision is higher than the EV of the best uninformed decision. This happens when posterior probabilities of the states given messages are higher than their prior. Otherwise, messages would be uninformative, not conditioning any appreciable change in the behavior of the WA.
4.2. Data Collection and Assessment Procedure
The usability of the information service is dependent on the accuracy of the messages provided by the information service itself and on what is at stake in the decisions. These elements contribute to determining the expected consequences of using the information. The sources of information needed to carry out the economic analysis are mainly based on: (1) information obtained by interviewing the WA; (2) information provided by the MOSES service; (3) additional ancillary information.
The first type of information is about the collection of primary data through an ad-hoc questionnaire. The questionnaire includes sections on: (i) WA information requirements; (ii) irrigation infrastructures (including details on water supply costs, efficiency of the supply system and on the amount of water delivered in each sector/district of the network); (iii) land use and cropping patterns (i.e. rain-fed and irrigated crop yields) and (iv) damages caused by extreme weather conditions (probability of a drought, expected damages per crop categories). The questionnaire helped to build the ICT informed decision model and to identify consequences of actions in states. With the joint use of secondary economic data on prices and yields from public databases (RICA–Rete di Informazione Contabile Agricola, 2017:
http://rica.crea.gov.it/public/it/index.php) and information on land use, damages, crop prices and costs and on water price and use, it was estimated that the economic payoff associated to consequences of actions in states. To simplify the assessment procedure, impacts of the decisions were estimated with the spatial limitation of the case study area.
The second type of information is about the new data provided by MOSES before and during the 2017 irrigating season. These are mainly crop water demand seasonal and in-season forecasts. Such data were provided with different spatial resolutions, then aggregated in functional management units (sectors of the irrigation network). The collection of such information allowed us to build a complete picture of the information environment which would have characterized the ICT-informed decision process of the WA in 2017.
The third type of information collected was needed to assess the accuracy of MOSES services. These are observed data in the form of: (i) aerial photos (provided by the WA); (ii) weather observation (available from MOSES meteorologists) and (iii) observed crop water requirements. The collection of such information is justified by the fact that the accuracy of the service is mainly dependent on three sources of uncertainty, contributing to the accuracy of the messages provided by MOSES: (1) crop maps; (2) water demand estimates, and; (3) forecasts. The accuracy of information was estimated from the hit rate of the service, coming from the ratio between the number of correct messages of the overall messages received by the WA. This ratio is a rough estimate of the probability of correctly predicting current and upcoming states. Specifically: (1) by comparing MOSES crop maps with aerial photos (provided by the WA), we calculated the probability that an irrigated crop mapped with MOSES satellite images matches with an irrigated crop mapped with aerial photos; (2) by comparing MOSES rainfall forecasts with rainfall observation, we calculated the probability that a forecasted rainfall above the estimated crop water requirements matches with the observed rainfall above the estimated crop water requirements. In addition, due to missing information, we assumed that, by comparing MOSES estimates of irrigation requirements with measured irrigation requirements, the probability that a positive irrigation requirement estimate (greater than zero) matches with a positive irrigation requirement measured with soil moisture sensors. Each of the above comparisons and assumptions contributed to the calculation of the probability of predicting a dry or a regular season before the irrigating season and the probability of predicting water requirements above or below a threshold value of 10 mm. This value is assumed to be the critical level influencing the amount of water to be supplied for each sector of the irrigation network during the irrigating season.
Appendix A provide all the information needed to test the assessment methodology for the estimation of the accuracy of information and the payoffs of the decision process.