As urban space continues to expand to accommodate a growing global population, there remains a real need to quantify and qualify the impacts of urban space on natural processes. The expansion of global urban areas has resulted in marked alterations to natural processes, environmental quality and natural resource consumption. The urban landscape influences infiltration and evapotranspiration, complicating our capacity to quantify their dynamics across a heterogeneous landscape at contrasting scales. Impervious surfaces exacerbate runoff processes, whereas runoff from pervious areas remains uncertain owing to variable infiltration dynamics. Increasingly, the link between the natural hydrological cycle and engineered water cycle has been made, realising the contributions from leaky infrastructure to recharge and runoff rates. Urban landscapes are host to a suite of contaminants that impact on water quality, where novel contaminants continue to pose new challenges to monitoring and treatment regimes.

Upgrading of large infrastructure is both expensive and disruptive, requiring large-scale excavation of surface areas including main road networks, so implementation of increasingly sustainable methods that capture stormwater runoff are favoure

There are several factors to consider when determining the opportunities for and constraints on the safe use, treatment and disposal of agricultural drainage water. Information and data desired at the site of drainage water production include: rate of drainage water production per unit area, chemical concentration of constituents of concern, and the rates of mass emission. Drainage water management requires additional information and data on drainage water quality and its suitability for the intended water uses as well as an understanding of environmental and health concerns. Upstream drainage water management affects the needs and water quality requirements of downstream water users. As reliable references are already available on estimating drainage water production volumes.

The geology of the region plays an important role in drainage water quality. Through weathering processes, the types of rocks (both primary and sedimentary) in the upper and lower strata define the types and quantities of soluble constituents found in the irrigated area. The oceans have submerged many parts of the continents during a period in their geological history. The uplift of these submerged geological formations and receding seas have left marine evaporites and sedimentary rocks behind, high in sea salts including sodium, chloride, magnesium, sulphate and boron. These geological formations exist in varying thicknesses, depths and extents on the continents. Through hydrological processes, solutes can enter the upper stratum by irrigation or floodwater, upward groundwater flow in seepage zones, with rising groundwater levels, or capillary rise. Once the solutes are in the upper strata, they influence the quality of agricultural drainage water through farmers' irrigation and drainage water management. The following example shows how the geology and hydrology of an area influence the quality of agricultural drainage water. It also illustrates the relationship between geomorphology, waterlogging and salinization.

Every catchment contributes uniquely in conformity with it's prevalent anthropologic activities. The naturally existing hydrologic cycle will remain unaltered safe the impact of human activities. Taking precipitation as the fuel that initiates the cycle, percolation and deep percolation inject a large amount of water into the sub surface with naturally existing terrain. However the appearance of paved surfaces; roads, runways, rooftops has immensely contributed to increased runoff, overtopping of drainage channels, flooding, which in turn affects the quality of water and it's availability. Modelling is capable of solving/ameliorating the afforementioned challenges when policy formulators are ready and willing to imbibe the culture of sustainable development by involving Water Resources Professionals in the development our environment

Reuse for agricultural crops. Modelling and its validity will depends the location and drainage needs? We never suggest everywhere we have use drainage. Its location, climate and trends of water logging needs to evaluate first at the project base and location specific.

A balanced ecosystem approach needs to look at the trade-offs between efficiency and reliability - these are fundamentals with application in many areas, including urban, water and catchment management. The article by Ulanowicz presents and illustrates these principles: Article Quantifying sustainable balance in ecosystem configurations

You are thinking in entirely different ways based on your model selection i.e long-term hydrology and water quality modelling. You must choose one and then proceed according to the objectives and study area (region).@Songjun Wu

You can check the effect of different drainage strategies using many models. For example, the DRAINMOD model is perfect in simulating various drainage strategies and its effects on the fate of both water and sediments in artificially drained lands. Using the DRAINMOD model will help in knowing the amount of water to be drained in a certain period of time (Days, months, or even years). Also, you can assess the amount of agricultural nutrients to be contained in drainage flux, thus you can assess the nonpoint source pollution of surface water resulting from drainage fluxes. Once you have these outputs, you can, for example, routing these sediments and assess the water quality in adjacent water bodies or even in the watershed scale using some models like the HECRAS model. Songjun Wu

Thank you all for the helpful answer!

Location, magnitude of the problem areas, goal of the region, priority of the local bodies, sociology, economics of the problem areas will determine the long run effect of reuse of drainage water. Apart from hydrology, weather and precipitation will be the necessary conditions for the long term success of the model but its sufficiency depends on the above mentioned factors also which we have experienced from hydrological studies from Asian countries mainly from Indian continent.

Hello,

Agricultural management and cropping patterns are also key to catchment hydrology and its modeling. You can have a look at our recent article:

Article Hydrological Response to Agricultural Land Use Heterogeneity...

cheers

Have you ever heard about WEAP ("Water Evaluation And Planning" system)?

Depending on your recsearch area and objectives it might be helpfull to consider human activity. It can be linked to other models or software.

https://www.weap21.org/index.asp?NewLang=EN