4. Results

After calibrating the model using real 2011 data and by estimating the calibration coefficients of the average cost function (Eq. (8)), the model was validated by running a status quo scenario and checking for consistency of the results compared to the observed values of land use. The result of this test showed that deviations of simulated land use variables (Xr,c,s) compared to the observed values of 2011 are all in the range of [1%, +1%] (Figure 2) meaning that the model is performing well [37].

This validation test shows that ASMOT is performing well and can thus be used for scenario simulation. The next step is to reformulate and modify appropriate equations in the model in order to be able to simulate the scenarios presented in Section 2.3. Economic, social, and environmental outcomes of these scenarios are presented in the following sections.

#### 4.1 Optimal land and water use under different scenarios

As discussed earlier, ASMOT optimizes the national agricultural value added and provides optimal regional land allocations for different crops and systems. These needed changes of land use in Tunisia allowing for optimal agricultural performances under a situation of water scarcity were purely calculated based on economic incentives corresponding to crop yields, costs, and incomes in the different regions and systems of Tunisia (Table 2). Results in Table 2 show the overall trend of land use under different scenarios (SC1, SC2, and SC3).

Table 2 shows that trends of SC1 and SC2 are consistent but in most cases different from trends suggested under SC3. For the case of cereals, both SC1 and SC2 suggest important cuts of cereal areas in NW and CW and an increase of these areas in NE and SO regions. However, cereal areas are suggested to be reduced in all areas (except SO) under SC3. The same scenario 3 is also more favorable for expanding olives, almond, irrigated fruit trees, and vegetable areas in the different

aggregated regions. The highest area reductions recorded under SC1 and SC2 are these of cereals in CW; irrigated fruit trees in NE, CW, and SO; and vegetable crops in the NE. Under SC3, the highest area reductions were however recorded for

Percentage change, compared to baseline situation, of the main crop areas under different scenarios (aggregated

Type of crops Regions Percentage deviations compared to the status quo situation

Cereal crops NW 0.28 0.06 0.75

Effects of Water Scarcity on the Performances of the Agricultural Sector and Adaptation…

DOI: http://dx.doi.org/10.5772/intechopen.83568

Olives and almond NW 0.8 0.4 1.6

Irrigated fruit trees NW 6.2 1.4 8.7

Vegetable crops NW 8.0 2.9 4.8

SC1 SC2 SC3

NE 2.21 0.77 1.39 CW 8.25 3.37 6.69 CE 0.01 0.03 0.14 SO 0.52 0.26 0.59

NE 3.8 2.1 3.3 CW 2.2 1.0 1.5 CE 0.1 0.0 0.1 SO 1.7 0.3 0.0

NE 8.0 3.8 0.2 CW 5.2 3.4 2.7 CE 0.7 0.6 3.4 SO 11.7 2.3 1.8

NE 17.0 7.3 5.4 CW 4.1 2.7 0.6 CE 7.5 2.7 7.5 SO 4.6 2.2 8.1

Total water use for irrigation under different scenarios in Tunisia was estimated based on optimal changes of land use as suggested in Table 2 (see Figure 3). In the baseline scenario, around 2086.6 million m<sup>3</sup> of water is used for the total irrigated area considered in ASMOT (78% of the total irrigated areas, around 352.9 thousand

third scenario, total water consumption, respectively, decreases to 1876.5, 1818.1,

these decreases led to average water consumptions of 5949, 5349.7 , and 5385.8 m<sup>3</sup>

corresponds to around 13% of the total water use in the baseline situation. These numbers are showing that effective water management in the irrigated areas in Tunisia can mitigate the effect of water scarcity and even generate agricultural

ha. Total water saving under the second scenario is about 268.5 million m<sup>3</sup>

economic growth if accompanied by appropriate economic incentives.

/ha (Figure 3). Under the first, second, and

/

, which

. By considering the new irrigated areas under each scenario,

cereals in CW and vegetable crops in NE.

changes of rain-fed and irrigated systems).

ha) with an average use of 5912.1 m<sup>3</sup>

and 1833 million m<sup>3</sup>

39

Table 2.

4.2 Irrigation water demand under different scenarios


Effects of Water Scarcity on the Performances of the Agricultural Sector and Adaptation… DOI: http://dx.doi.org/10.5772/intechopen.83568

#### Table 2.

• Scenario 3. Cutting total fresh water availability by 25%, in addition to an increase of IWUE with 10% and higher producer prices offered to farmers. The suggested increase of producer prices are as follows: +5% for cereal prices and

After calibrating the model using real 2011 data and by estimating the calibration

As discussed earlier, ASMOT optimizes the national agricultural value added and provides optimal regional land allocations for different crops and systems. These needed changes of land use in Tunisia allowing for optimal agricultural performances under a situation of water scarcity were purely calculated based on economic incentives corresponding to crop yields, costs, and incomes in the different regions and systems of Tunisia (Table 2). Results in Table 2 show the overall trend

Table 2 shows that trends of SC1 and SC2 are consistent but in most cases different from trends suggested under SC3. For the case of cereals, both SC1 and SC2 suggest important cuts of cereal areas in NW and CW and an increase of these areas in NE and SO regions. However, cereal areas are suggested to be reduced in all areas (except SO) under SC3. The same scenario 3 is also more favorable for expanding olives, almond, irrigated fruit trees, and vegetable areas in the different

Percentage deviation of simulated vs. observed crop areas in different regions included in the ASMOT model.

coefficients of the average cost function (Eq. (8)), the model was validated by running a status quo scenario and checking for consistency of the results compared to the observed values of land use. The result of this test showed that deviations of simulated land use variables (Xr,c,s) compared to the observed values of 2011 are all in the range of [1%, +1%] (Figure 2) meaning that the model is performing well [37]. This validation test shows that ASMOT is performing well and can thus be used for scenario simulation. The next step is to reformulate and modify appropriate equations in the model in order to be able to simulate the scenarios presented in Section 2.3. Economic, social, and environmental outcomes of these scenarios are

+10% for fruits and vegetable prices.

Agricultural Economics - Current Issues

presented in the following sections.

4.1 Optimal land and water use under different scenarios

of land use under different scenarios (SC1, SC2, and SC3).

4. Results

Figure 2.

38

Percentage change, compared to baseline situation, of the main crop areas under different scenarios (aggregated changes of rain-fed and irrigated systems).

aggregated regions. The highest area reductions recorded under SC1 and SC2 are these of cereals in CW; irrigated fruit trees in NE, CW, and SO; and vegetable crops in the NE. Under SC3, the highest area reductions were however recorded for cereals in CW and vegetable crops in NE.

#### 4.2 Irrigation water demand under different scenarios

Total water use for irrigation under different scenarios in Tunisia was estimated based on optimal changes of land use as suggested in Table 2 (see Figure 3). In the baseline scenario, around 2086.6 million m<sup>3</sup> of water is used for the total irrigated area considered in ASMOT (78% of the total irrigated areas, around 352.9 thousand ha) with an average use of 5912.1 m<sup>3</sup> /ha (Figure 3). Under the first, second, and third scenario, total water consumption, respectively, decreases to 1876.5, 1818.1, and 1833 million m<sup>3</sup> . By considering the new irrigated areas under each scenario, these decreases led to average water consumptions of 5949, 5349.7 , and 5385.8 m<sup>3</sup> / ha. Total water saving under the second scenario is about 268.5 million m<sup>3</sup> , which corresponds to around 13% of the total water use in the baseline situation. These numbers are showing that effective water management in the irrigated areas in Tunisia can mitigate the effect of water scarcity and even generate agricultural economic growth if accompanied by appropriate economic incentives.

decrease of total water use under this scenario. In fact, irrigated areas will decrease the most under SC3, and the average water use by hectare of irrigated land will also be 9.5% lower than SC1. Furthermore, the average price inflation considered under SC3 is only about 7.5%, with a maximum of 10% for vegetables and fruits. This price increase generated a higher and nonproportional increase of the value added (+13%), showing a relevant and positive and environmental effect of this price

Effects of Water Scarcity on the Performances of the Agricultural Sector and Adaptation…

Figure 5 shows a geographical distribution of changes in total agricultural value added among the considered regions, under different scenarios. It also shows the respective trends of these values among rain-fed and irrigated sectors. The figure shows that irrigated agriculture in Center West and North East of Tunisia is mostly affected by water scarcity. However, the contribution of the rain-fed agriculture in these two regions is also expected to grow which will partly overcome the

In this section we provide an overview of changes in labor demand under different scenarios compared to the baseline situation. Figure 6 shows that despite the optimization of land use and agricultural value added, agricultural labor

Changes of regional agricultural value added under different scenarios in Tunisia (million TND).

negative effects of the decrease of irrigation value added.

4.4 Social effect of water scarcity scenarios

DOI: http://dx.doi.org/10.5772/intechopen.83568

instrument.

Figure 5.

41

Figure 3. Total water use for irrigation under different scenarios.

### 4.3 Impact on agricultural value added

ASMOT provides information about the total value added of its respective agricultural land area as the most aggregated results calculated based on optimization of these values at regional levels. This result can be calculated and presented for separate scenarios. For our particular case, the optimization process shows that Tunisia can overcome the problem of water scarcity (Figure 4) through specific structural changes of land use among crops, systems, and regions, as suggested in Table 2. Figure 4 shows that agricultural value added in Tunisia will decrease with only 0.76 and 0.16%, respectively, under SC1 and SC2. However, these slight changes can only be possible if structural adaptations of the Tunisian agricultural sector, based on specific land use reallocations, are adopted as shown in Table 2.

Scenario 2 shows that with 10% increase of IWUE, the cut of water availability can be effectively mitigated, with an agricultural value added remaining almost equal to the status quo situation. If producer prices will further be supported (+5% for cereal crops and +10% for fruits and vegetable crops), the agricultural value added in Tunisia can even be 13% higher than the baseline situation, despite the sharp water cut considered. This higher value added of SC3 is not only due to the suggested price inflation but also to the restructuring of land use and the

Figure 4. Effect of water scarcity scenarios on the national agricultural value added.

## Effects of Water Scarcity on the Performances of the Agricultural Sector and Adaptation… DOI: http://dx.doi.org/10.5772/intechopen.83568

decrease of total water use under this scenario. In fact, irrigated areas will decrease the most under SC3, and the average water use by hectare of irrigated land will also be 9.5% lower than SC1. Furthermore, the average price inflation considered under SC3 is only about 7.5%, with a maximum of 10% for vegetables and fruits. This price increase generated a higher and nonproportional increase of the value added (+13%), showing a relevant and positive and environmental effect of this price instrument.

Figure 5 shows a geographical distribution of changes in total agricultural value added among the considered regions, under different scenarios. It also shows the respective trends of these values among rain-fed and irrigated sectors. The figure shows that irrigated agriculture in Center West and North East of Tunisia is mostly affected by water scarcity. However, the contribution of the rain-fed agriculture in these two regions is also expected to grow which will partly overcome the negative effects of the decrease of irrigation value added.
