Three millennia ago, a Greek philosopher, Thales of Miletus had claimed that 'best of everything in this universe is water'. UN conference 1977, first time declared water as a basic need of living being which was sealed by UN Resolution Act 64/292. Additionally, the general assembly of UN in 2010 recognized water supply and sanitation (WATSAN) as the human rights .

Undoubtedly, it is no surprise that access to water has been a global development priority since many decades. Despite priorities given, above two billion population facing water scarcity by 2025 and annually 300 million cases of diseases related to water are reported with 5% deaths. Unplanned urbanization is expected to cause perennial water shortage to one billion people in poor nations by 2050. Also, as little as 30% of the global cultivated area is irrigated till now (ICID 2023) and is predicted that the availability of freshwater in agriculture will decrease globally by 17%. The Global Water Security Assessment 2023 alarming that world is out of track to meet its SDG goals in water. In the context of changing climate, shooting population and the corresponding competition among users, FAO (2019) recommends to improve the understanding of global water supply and demand. These literature evidences highlight the importance of single drop of water managing water as a finite and scarce resources which needs to be rationalized its use in terms of productivity, efficacy and access. In this context, the overall aim of this article is to review, document and analyze the current status of water, challenges, opportunities and way forwards for its sustainability to uphold food security.

The water bodies are regarded as the strategic catalysts for development and life of any nation and hence, water is becoming a national security issue for powerful countries. Availability of water indorse food production and nutrition, urban development and industrialization, income generation and livelihood, and human health and hygiene. Food security is the first priority of every government in which water plays a detrimental role. The World Food Summit (1996) defined food security as 'when all people , at all times, have physical, social and economic access to sufficient, safe and nutritious food to meet dietary needs for a productive and healthy life'. The country having enough water means it has secured the future which is directly associated with national security. one of the UN general secretaries and many other scholars and pointed that due to geo-hydro politics, the conflict between states and countries is inevitable in future which indicates that water is directly/ or indirectly related to the national security.

In a global context, the FAO (2019) believes that there is a world food shortage which can only be alleviated if agricultural productivity can be increased in significant and sustainable fashion via expansion of irrigation coverage and improvements in water management. Agriculture consumes almost 70% of the global freshwater withdrawals, however, in many areas of the world, municipal, industry and environment sectors putting pressure to constrain the share of water in irrigation. In such situations, food security is only possible if a) the current productivity level of agricultural water is improved and, b) introduction of new and non-conventional sources of water and drought-resistant crop varieties come into sustainable practice. In recent years, agricultural farms throughout the world have been subjected to increasing water constraints. Major droughts in Chile and the US have affected crop production while diminishing surface and groundwater reserves.

Agriculture is the backbone of national economy in Nepal which depends largely on monsoon rains. The majority of arable area has some sort of irrigation facilities but below 35% of irrigated land gets year-round water. For the agricultural transformation from subsistence-based to a sustained industry, the crop parameters including production and intensity have important role. One of the major challenges in Nepalese agriculture sector is to increase 50% yield per unit of land which can only be fulfilled through the improvement of cropping intensity and introducing high yielding hybrid varieties that subsequently demands more water. In another side, water availability in Nepalese farm continues to remain a barrier for production of cereals and horticultural commodities resulting millions dollars outgoing in food import. Despite huge potential of freshwater resources in Nepal, we are unable to transform our agriculture into a profitable and sustainable enterprise. For making agriculture more commercial, cost reduction including water, energy and nutrients should be made possible. Increasing irrigation efficiency makes farm operations more economically viable whereas conserving water saves money through reduced pumping cost. As agriculture is the base of Nepal, innovative and practical measures for higher productivity in irrigation including integrated crop-water management has utmost importance. Mishra warned that food security issues will not be managed until water efficiency and efficacy in agriculture will be improved.

In the drum of global available water, less than 3% is freshwater and nearly 1% of that is readily available. The annual renewable water resources throughout the world amount to nearly 50,000 km3 and currently 70% of the available freshwater is being used where rule is rate of water use should be maintained at a lower than the renewable rate for sustainability. Also, climate change is becoming a threat putting pressure on water, its quantitative availability and quality for nature-positive agriculture/ economic development. To tackle these challenges associated with water, Mishra recommended some important solutions including technological advancement, identification of new sources and modernization of management techniques. Furthermore, Hashem et al. added that using alternative sources of water (particularly recycled water) and employing efficient irrigation strategies including private sector participation are the two immediate remedies in water sector.

Recycled water is currently being used in many countries for amenity agriculture application, and parkland irrigation which reduces reliance on rainfall. However, published literatures reveal that wastewater reuse can cause questions regarding to human and environmental health which can be answered through suitable treatment practices, careful use and regulations. According to FAO, treated wastewater from 5 lakh people has capacity to irrigate 6000 ha agricultural land with extra advantages of fertilizers (N - 250 kg/ha, P- 50 kg/ha & K - 150 kg/ha. year). Thus, all of the nitrogen and much of the phosphorus and potassium normally required for crop production would be freely supplied by the recycled wastewater. Australia and developed nations have secured water via the production and effective application of recycled water in agriculture.

One of the global problems in water is repair, maintenance and modernization of the old infrastructures which needs huge financial investment. In this context, private sector participation could be one of the approaches to help achieving UN targets in water-SDGs. The PPP concept in the water was initiated from the French historical model of public service delegation and currently it serves water to 5% of the world's population, and private financing in WATSAN accounts for 10% of the sector's total investment. These authors have pointed three major bases why states have to give importance to PPP in water sector: a) budget limitation in government, b) Better efficiency and performance of private parties in the same cost, and c) Higher risk management capacity of private compared to public sector. Undoubtedly, developing countries throughout the world including Nepal are giving priority to PPP in their sectorial policy of water (irrigation, hydropower, drinking water and environment). The World Water Council's Vision 2025 assumes that around USD 3000 billion needs to be invested over a 25-year period in water sector which anticipated 70% private sector's contribution to meet the target.

Seven out of 17 SDGs (1, 2, 3, 6, 13, 15, and 17) of UN Agenda 2030 are directly or indirectly related to water which are forcing us to conclude that water is the key factor for the economic prosperity because any developmental activities demands water as a main component of hardware. It is said that earth contains enough water for living being but there is water insufficiency, primarily due to mismanagement, bureaucratic inertia and limited financial and human resources. Water is an indispensable ingredient to agricultural production and without water, growers would not be able to produce crops and feed their animals. Therefore water insecurity reflects food insecurity. A shift towards more nutritious and healthier diets will have repercussion on water consumption that cannot be ignored. Some of the healthy food we need, particularly fruits and vegetables, requires a sufficient amount of good quality water to be produced. Government policies need to tackle water risks to make water available for food production and to ensure that agricultural production does not pollute water sources. Strategies of 3R (reduce, recycle and reuse) should be practiced in all the fields where water goes. Also, the current and the foreseeable trend indicates that water problems will continue to become increasingly complex and more intertwined among competitors. So, this author believes that water should not be viewed in isolation by one organization which demands IWRM strategy, applying knowledge from various stakeholders to devise and implement efficient, equitable and sustainable solutions to improve water productivity. In such condition only, a balance can be established between personal and economic needs which not only ensures the sustainability of ecosystems but also helps achieving the slogan of FAO 2023: 'water is life, water is food. Leave no one behind'.

Dr Chand is a senior agriculture engineer at Prime Minister Agriculture Modernization Project