Increase of economic and productivity efficiencies intensifies environmental pressures, too. Agriculture is one of the most common examples of this phenomenon. The sector is lacking proper management, which is especially prominent in Mediterranean areas. To address the situation, a holistic modeling approach, combining hydrological, economic and water quality aspects, is recommended for implementation in a Greek watershed. The broader area is degraded regarding its water availability, quality, and management. The model provides insights into water balance, net profit from agricultural activities, presents water quality data from simulations, and introduces two useful parameters informing the decision-maker's knowledge and understanding: the deficit irrigation water's value and a hydro-economic index which estimates (socio-)economic benefits over environmental balance. A combined demand-management plan is also examined considering the above outputs in investigating the multiple effects of the suggested policy measures. Furthermore, to discuss the optimal approach depending on data availability and scope, we compare two different settings of the proposed model. The results of the study confirmed the continuous quantitative and qualitative water resources' deterioration and economic overexploitation of the watershed. The study reveals the immediate need for management actions, integrated modeling approaches, and provides future recommendations on hydro-economic modeling.