The Indus River Basin covers an area of around 1 million square kilometers and connects four countries: Afghanistan, China, India, and Pakistan. More than 300 million people depend to some extent on the basin's water, yet a growing population, increasing food and energy demands, climate change, and shifting monsoon patterns are exerting increasing pressure. Under these pressures, a ''business as usual'' (BAU) approach is no longer sustainable, and decision makers and wider stakeholders are calling for more integrated and inclusive development pathways that are in line with achieving the UN Sustainable Development Goals. Here, we propose an integrated nexus modeling framework co-designed with regional stakeholders from the four riparian countries of the Indus River Basin and discuss challenges and opportunities for developing transformation pathways for the basin's future.

This paper focuses on the scope of conjunctive management in the Lower Indus part of the Indus Basin Irrigation System (IBIS), and the contribution this could make towards food security and socioeconomic development. The total Gross Command Area (GCA) of the Lower Indus is 5.92 Mha, with a cultivable command area (CCA) of 5.43 Mha, most of which is in Sindh Province. There is a limited use of groundwater in Sindh (about 4.3 Billion Cubic Meter (BCM)) for two reasons: first, there is a large area where groundwater is saline; and second, there is a high surface irrigation supply to most of the canal commands, e.g., average annual supply to rice command is 1723 mm, close to the annual reference crop evapotranspiration for the area, while there is an additional annual rainfall of about 200 mm. These high irrigation allocations, even in areas where groundwater is fresh, create strong disincentives for farmers to use groundwater. Consequently, areas are waterlogged to the extent of 50% and 70% before and after the monsoon, respectively, which contributes to surface salinity through capillary rise. In Sindh, about 74%-80% of the available groundwater recharge is lost in the form of non-beneficial evaporation. This gives rise to low cropping intensities and yields compared to fresh groundwater areas elsewhere in the IBIS. The drought of 1999-2002 has demonstrated a reduction in waterlogging without any corresponding reduction in crop yields. Therefore,

I. INTRODUCTION Water is important natural resource which covers 70% of earth that exists on planet of earth and without it, life cannot survive. The major human activities have been used for polluting fresh water bodies. About 1.5 billion people have no safe drinking water globally and about 5 million deaths per year are attributed due to waterborne diseases [1]. It is estimated that 70% of industrial wastes in developing countries are disposed of untreated into waters where they contaminate existing water supplies [2]. The UN also estimates that the amount of wastewater produced annually is about 1,500 km 3 , i.e. six times more water than exists in all the rivers of the world [3]. The effluents from sugar mills are discharging without

Participatory irrigation, where farmers are given greater control and management responsibility, has been a topic of controversy for many years. Initially seen as a panacea for dealing with weaknesses in state-run irrigation, participatory irrigation has generated mixed results, especially in South Asia. Part of the challenge of understanding the conditions that promote and undermine participatory irrigation is that it is seldom deployed in the same way. For example, irrigation fees collected by farmers are not handled in the same manner, even within a single country. In some instances, a large portion of collected monies is retained locally and in others, only a small portion is kept for local use. In this paper, we use game theory to contemplate how the portion of irrigation fees retained locally might impact on the effectiveness of participatory irrigation. We show that there are multiple plausible equilibria, and that allowing farmers to retain more funds locally might shift behaviour from an uncooperative equilibrium to a cooperative outcome. However, we also find that it is unlikely for there to be a singular fix and we use empirical evidence to demonstrate the conundrums of making participatory irrigation sustainable.

The Mehran model is developed based on the FAO-56 modified Penman-Monteith equation for computing reference and crop evapotranspiration with dual crop coefficients. Evapotranspiration (ET) of wheat in three field experiments with management-allowed depletion (MAD) of 45, 55 and 65% was observed through gypsum block readings and a drainage lysimeter. The seasonal crop ETs were observed as 363, 359 and 332 mm, and were computed as 383, 369 and 355 mm. The corresponding water use efficiencies (WUEs) were ascertained as 14.1, 15.0 and 13.4 kg (ha mm)À1 . The highest crop WUE was achieved with MAD at 55%; therefore, this research is more focused upon in the paper. The model relatively overestimated seasonal ET by 2.8%. Weekly root length and daily soil-moisture measurements revealed that wheat extracts most of its moisture from the 0-50 cm soil profile. When practising either scientific or traditional irrigation scheduling in the country, a seasonal water amount of 370 mm is suggested for wheat to achieve optimum yield and WUE.Statistical analysis (R 2 ¼ 0.90, T ¼ 2.09, and F ¼ 999) showed good correlation between computed and actual seasonal ETs of crop with an experimental MAD of 55%. The Mehran model is found to be quite versatile and can be successfully used as a decision support system (DSS) for irrigation scheduling of wheat in Pakistan. L'analyse statistique (R 2 ¼ 0.90, T ¼ 2.09, et F ¼ 999) a montré la bonne corrélation entre l'évapotranspiration saisonnière calculée et réellement mesurée pour une irrigation rationnée à 55%. Le modèle de Mehran apparaît tout à fait souple et peut être employé avec succès en tant que système interactif d'aide à la décision pour le pilotage de l'irrigation du blé au Pakistan.