Study Site and Decision Problem

A real-world water management problem implemented in this thesis refers to a typical situation of a coastal agricultural region in an arid environment. Arid and semi arid regions – which receive relatively low overall amounts of precipitation in the form of rainfall or snow – cover approximately 40% of the Earth’s land area, and support 2 billion people, 90% of whom live in developing countries (UN, 2011). Water scarcity, over-exploitation of groundwater, incomplete information about groundwater recharge, inefficient irrigation and saltwater intrusion in coastal areas are among typical water-related problems in those regions. These challenges are further exacerbated by climate change and ever increasing population.

The study is oriented on the specific situation of the Al-Batinah region in northern Oman. It is intended to contribute towards the development of integrated water resources' management strategies for an agricultural coastal plain which is being affected by saltwater intrusion driven landward due to excessive groundwater extraction for irrigated agriculture, threatening the economic basis and associated social activities.

The general description of the study area is shown in Fig. 18, indicating wadis (intermittent streams) originating from the Hajar Mountains and running into the coast, artificial recharge dams and a number of groundwater abstraction wells. The study area covers an area of about 2460 km² which extends over some 30km broad coastal plain bordered by the Gulf of Oman (the Sea of Oman) and the Hajar Mountains.

The Al-Batinah represents one of the major settlement areas in Oman (with almost 65% of the nation’s population (ca. 800,000 inhabitants)) living in this region. In addition, one-third of economically active population of the nation is working in the agriculture sector underlying its importance for the society. As soils are especially fertile in the coastal plain, agriculture plays an important role in this region. This in turn led most of the available water resource to

be used for agricultural purpose (ca. 90%), followed by small amounts for portable water and industrial usage (Al-Shaqsi, 2004).

Figure 18: Study catchment in Al-Batinah region, Sultanate of Oman.

Due to arid climatic conditions, agriculture production hugely depends on irrigation. The substantial part of this water is obtained from the local coastal aquifer system by a large number of uncontrolled hand-dug and drilled wells, except a small proportion gained from desalinization (Walther et al., 2012).

An extensive irrigated agricultural practice in the coastal plains since the 1980s coupled with currently applied inefficient irrigation activities has resulted in major groundwater abstraction rates which in turn led to declining groundwater levels. In the 1970s it is assumed that the abstraction rates were constant at about 30Mm³/year, while current abstraction rates are estimated at about 120Mm³/year (Walther et al., 2012). Rainfall generated in the mountain area in the south of the study catchment is the main enhancement of natural groundwater.

The estimation of various sources show that the mean average precipitation in the study area range from up to 350 mm/year in the Hajar Mountain to 50mm/year along the coast with wide variations. Sustained periods of above-average and below-average rainfall are observed. As a result, persistence of dry years is considered to be one of the major

7 Application: Integrated Modeling Approach for Supporting Management Decisions of Coupled Groundwater-Agricultural Systems (Oman)

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challenges for effective water resources management. The approximated recharge from the mountains into the aquifer system is only 50Mm³/year (Gerner et al., 2012). Significant disproportion in the current abstraction rate (ca.120Mm³/year) and replenishment level (ca.

50Mm³/year) led to a considerable negative water balance since late the 1970s followed by an alarming decline of groundwater levels accompanied with saltwater intrusion into the coastal aquifer (Walther et al., 2012). Continuous decline in groundwater levels cause the natural groundwater gradient to reverse leading to intrusion of seawater into the aquifer and consequent gradual soil salinization. Particularly in the coastal plain of the study area, shallow wells of small farms and household run dry, to the extent that people abandon their farms and therewith endangering associated socio-economic conditions as well as traditional social structure.

Some management interventions have been already undertaken by the government in order to improve the situation. Exemplarily, these interventions refer either to the water resources side by building artificial groundwater recharge dams in order to use surface water runoff more efficiently for recharging the aquifer or to the water demand side by implementing measures like stop of drilling new wells or shifting the cultivation of fodder crops with high water demands more inland. However, the situation remains still worse and may require more drastic management interventions which may range between the extremes of stopping all agricultural activities in order to recover the local aquifer system or producing as much as possible as long as water and soil resources will be available (sustainable aquifer vs. high profitable agricultural production). Due to the nonlinear behavior of the coupled physical processes of the coastal aquifer-agriculture hydrosystem and its interactions with numerous decision makers (farmers, governmental agencies, etc.), which have different, sometimes contradicting, interests and views on how to manage the system in the best way, the decision-making problem is very complex. Finally, only a combination of different measures or management interventions will yield to an improvement of the situation.

Based on the description and discussion above, the following conclusions can be drawn regarding the water resources management in this setting:

 Management of the interacting groundwater-agricultural hydrosystems has to consider different socio-economic and environmental issues as well as viewpoints of involved stakeholder in addition to the physical processes.

 Presence of incommensurable and conflicting objectives inherent in the coupled groundwater-agricultural hydrosystems require the development of tools that have the capability to integrate diverse knowledge in a unified operational framework to support the decision-making process of finding appropriate management interventions or policies under uncertainty.

 We do not know everything how different interacting processes (hydrological, economic, social and environmental) and their feedbacks work, and that even if we do know how things work, it is highly likely they are going to change. This implies learning should be embodied in managing coupled groundwater-agricultural systems in a way that to build social learning so that shared agreement and trust among society to act collectively in addition to understanding how things work.

To contribute towards here above discussed water resources management decision problems and to achieve the intended goals, the two new integrated modeling approaches proposed in this thesis in the preceding sections – BN-based decision support tool (chapter 5) and fuzzy-stochastic multiple decision analysis tool (chapter 6) – have been implemented in the study area and are presented in the following sections.