## 5 Application to Case Study and Discussion
### The Artificial Readrage Program in Agua Amarga  
The Agua Amarga coastal aquifer has been subjected to anthropogenic intervention during the last century [36]. The artificial recharge of the aquifer over the protected salt marsh surface has been carried out regularly since 2008. This measure compensates for the negative effect on piezometry caused by groundwater abstraction from the pumping wells of the Alicante desalination plants. The measure has proven to be environmentally sustainable and has provided alternatives for salt marsh enhancement.  
The verification of the type curves is applied to a 2D cross-section in the direction of the general flow and includes the piezometer P-8 located at the border of the flooded ponds (the recharge area) and the piezometer D-2 (Figure 10). The depression cone is located to the north, where 26 pumping wells are arranged parallel to the coastline.  
In this case study, the recharge volume over the salt marsh (I\({}_{\text{r}}\) = 350 m) was compared to that estimated from the temperature-depth profile in D-2, using a piezometer in the flow direction that was close enough to the marshes (390 m from the right border of the marshes) to ensure that the characteristic thermal length was larger. A period of constant recharge was selected (the year 2020), and a month in which the temperature-depth profile and the flooded ponds were known was chosen (October 2020). The flooded marshes had a width of approximately 100 m. The distance between the left boundary of the cross-section  
Figure 9: Flow diagram of the inverse problem.  
and the piezometer D-2 was 740 m. From the dimensionless temperature in Figure 11 and the universal set of curves in Figure 7, x/l\({}_{\rm T}\) = 0.60 was obtained; therefore, a length of l\({}_{\rm T}\) = 1233 m was obtained. This value was taken as \"L\" since it can be stated that, from this length, the groundwater flow is horizontal and, consequently, the thermal profiles are not affected by the recharge flow from the marshes. By using the universal curve (Figure 12, which had to be designed for this scenario due to the large value of the \(\frac{l_{\rm L}}{H}\) ratio, for the case when l\({}_{\rm r}\)/H = 8 (for H = 44 m), a value of \((\rm k_{m})/(\rho_{\rm e,w}c_{\rm e,w}\cdot k_{\rm Y}\cdot\Delta h)\) = 0.0035 was obtained. Considering k\({}_{\rm m}\) = 2.7 cal/(s\(\cdot\)m\(\cdot\)\(\circ\)), \(\rm e_{\rm e,w}c_{\rm e,w}\) = 10\({}^{6}\) cal/(m\({}^{3.\circ}\)C), and \(\Delta h\) = 6.17 m (since the gradient equals 0.005), a vertical hydraulic conductivity \(\rm k_{y}\) = 10.8 m/d was obtained. Thus, the horizontal hydraulic conductivity was \(\rm k_{x}\) = 108 m/d.  
Figure 11: Universal temperature profiles within the characteristic length. The dashed line represents the universal temperature profile non-dimensionalized value in piezometer D-2 in October 2020.  
Figure 10: (**a**) Study area showing the D-2 piezometers, the recharge ponds in the salt marsh, and the groundwater flow direction in the Agua Amarga coastal aquifer (Google Earth). The dimensionless temperature–depth profile of D\(-\)2 in October 2020 is depicted on the right (**b**).  
Figure 4 can now be used to estimate the dimensionless flow rate \(\frac{\mathrm{Q}}{(\mathrm{h_{2}}\mathrm{-h_{1}})\sqrt{\mathrm{K_{x}}\mathrm{K_{y} }}}=0.151\), giving a value of \(\mathrm{Q}=32.82\) m\({}^{2}\)/d in the cross-section. Assuming 100 m of transversal extension (the pond stretch), the recharge flow from the irrigation marshes to the aquifer that reaches the piezometer D-2 is 3282 m\({}^{3}\)/d. In this month, the artificial recharge was 4167 m\({}^{3}\)/d, which was 80% of the estimated recharge.